Why lemurs get sick: A lesson for humans, too

Female blue-eyed lemur

What lessons can humans learn from our far distant prosimian primate cousins about living well and eating a healthy diet?

This was the question on my mind as I toured the Duke Lemur Center in Durham, North Carolina with colleagues attending Science Writers 2012. (Read Christie Wilcox’s full report about our tour over at Science Sushi on Scientific American.)

When I learned on the tour that lemurs were getting sick, I inquired further from our tour guides, education associate Chris Smith and education manager Niki Barnett. The thought of these adorable creatures—somehow related to me because of a common ancestor some 50 to 80 million years ago—suffering from the same types of chronic diseases as modern-day humans encouraged me to want to find out more about their care and treatment.

Lucky for me, Chris, who might’ve tired from me badgering with so many questions, helped me arrange an interview with the center’s senior veterinarian. On my second visit to the center at a later date, Dr. Cathy Williams described for me, and showed me, what it was like to work as a clinician in the world of lemurs.

Lemurs and humans, not so different

There are multiple parallels between why humans get sick and why the lemurs do, Dr. Williams told me.

"They mainly have to do with diet," she said. The diets for lemurs at the center are not necessarily ideal—even in this magical place, home to the largest population of the world's most endangered primates outside of Madagascar.

Routine physical exams and dental cleanings make up most of a day in the life of a senior veterinarian, Dr. Williams told me. The veterinarians and keepers work hard to make life for the lemurs as healthy and comfortable as possible.

Sifakas eat primarily leaves

I was interested to find out that captive lemurs often get a lot of tartar build-up on their teeth while wild lemurs do not. The reason is mainly because the diets of captive lemurs are mainly composed foods that are often much higher in sugars and starches than in Madagascar.

"There is less fiber, the fruits are softer, and there’s less chewing and pulling leaves from trees," Dr. Williams said. Chewing and pulling in the wild act as nature’s way of brushing and flossing, Dr. Williams said, "We see a lot of gum diseases. I’ve never seen that in the wild at all." 

Dental care

Lemurs in the center receive dental cleanings every couple of years. If one of the animals has dental problems, they get cleanings more often. Dr. Williams also encourages behavioral trainers to regularly floss the teeth of the lemurs, time and human-power permitting.  

Similar to lemurs, dental caries are somewhat of a novelty among humans, according to Randolph Nesse and George Williams. The authors of Why We Get Sick: The New Science of Darwinian Medicine wrote that tooth decay and cavities only became more common because of today’s frequent and prolonged exposure to starches and sugars that feed the bacteria responsible for producing acid that causes demineralization of teeth.

Caries exist in alongside a long list of chronic health-related problems caused by "modern dietary inadequacies and nutritional excess," Nesse and Williams write. Others we're all familiar with are obesity and diabetes.

Choosing appropriate foods

Blue-eyed lemurs and sifaka play together, but have different diets.

When I asked Dr. Williams if obesity was a growing problem among captive lemurs, she said that it was, although not so much at the center.

Because the center is in the habit of loaning animals out to other zoos around the country, they've seen obesity become a problem in part because of the difficulty in training zookeepers on how to appropriately feed the lemurs appropriately.

The major challenge, she said, is in simply educating keepers to understand that feeding strategies are different for different species of lemur. All lemurs are similar in that they are herbivorous hindgut fermenters having simple stomachs and large cecums (as opposed to foregut fermenters, which are generally ruminant species like cows); however, intestinal transit times between lemurs vary greatly.

On one end of the spectrum, you have the red-ruffed lemur. In this species, the intestinal transit time is short, so fermentation in the cecum is bypassed. Their feeding strategy is to eat easily digestible foods, and a lot of them. They primarily eat a lot of fruits, but don't absorb a lot when they do. "The joke goes: it goes in a banana, it comes out a banana," Dr. Williams said.

On the other side of the spectrum, there are bamboo lemurs and sifakas with long intestinal transit times. These lemurs eat primarily leaves and rely on their fermentation for production of short-chain fatty acids to supply the majority of their energy (similar to gorillas versus chimps). In comparison, the ring-tailed, brown and blue-eyed lemurs tend to be more generalist in eating a variety of leaves, fruits, and some insects. Ring-tailed lemurs may even make a meal out of a small bird on occasion.

Many of the problems result from insufficient knowledge or misunderstanding on the part of zookeepers. If a red-ruffed lemur is put on a diet of leaves, the animal won't absorb enough nutrients to survive for very long. Conversely, if a sifaka is fed a diet high in fruit, the diet will favor growth of microflora that uses starch more efficiently and doesn't ferment fibers well; the resulting changes in pH alone will give the animal diarrhea until its probable death.

To prevent sickness and death of animals that are on loan, Dr. Williams said zookeepers are now required to come to the center to be trained, "They'll learn that, yes, sifakas like banana, but, no, we can't feed it to them. Yes, they will eat it, but it's not good for them."

Controlling portions and low-glycemic foods

Ringtailed eat a mix of fruits, leaves, insects, and even birds.

Earlier this year, it was at one of these Prosimian Husbandry Workshops where Dr. Williams shared new information with zookeepers on what feeding strategies in the center have been used to help prevent or control obesity and diabetes.

One important bit of knowledge Dr. Williams passes on is that "when we say 'frugivore,' we're talking about a wild diet that is very high in fiber, low in starches. But when folks think 'frugivore' in captivity, they think apples, bananas, and grapes—these are not at all like fruits in the wild."

Lemurs at the center are never overfed, Dr. Williams told me, but diabetes is still a significant issue. "The diabetics in our colony were never obese, but we're still causing problems that lead to insulin resistance," she said. In addition, kidney failure and cancer are other main causes of death.

Much in the same way humans might like "marshmallows and chocolate eclairs," as Nesse and Williams write in their book, the problem with lemurs is that they have "mismatch of tastes evolved for stone age conditions."

All lemurs enjoy the types of fruits and starchy vegetables we've cultivated for our taste buds, Dr. Williams said, which can easily lead to overfeeding with these kinds of foods and that can lead to obesity and diabetes.

Lemur care, age, and inflammation

Once an animal has diabetes, it must be controlled with a low-glycemic diet—consisting of leaves and primate biscuits that are higher in fiber, lower in starch and sugar—alongside anti-diabetic medications such as metformin.

                                                                                                                      

I asked Dr. Williams how the lemurs responded to being put on their low-glycemic biscuits versus their normal, more palatable, sugary, cookie-like treats. She said they responded in the same way as a human would after hearing, "OK, you're not eating anything but bran and leafy greens for now on." Not very well at all.

Why can't I play outside?

There are several contributing factors to chronic disease in lemurs, Dr. Williams said. One may be simply be age, since the animals at the center, depending on the species, can usually live well into their 20s and 30s, which is not normal in the wild.

These older animals also have limited mobility, resulting from age-related wear and tear, and are not able to enjoy some of the free-range enclosures the lemur center provides. A more sedentary lifestyle indoors can lead to less insulin sensitivity and, while the center does offer enrichment programs to encourage activity, Dr. Williams notes, the rewards used in these programs is usually sweet treats.

Seeking the ideal lemur diet

                                                                                           

How these aging lemurs are fed and what they're fed in their diets are still not what Dr. Williams would consider ideal. "It could be better," she said; for instance, the lemurs usually receive all their food in one or two feedings daily while, in the wild, they generally graze throughout the day. More feedings over the course of the day may help stabilize blood sugar.

In addition, Dr. Williams has noted mild, low-grade inflammation is a factor. As part of her clinical duties, she performs autopsies whenever a lemur dies. Histopathological exams of tissues upon death often reveal a mild chronic colitis or hepatitis. "We don’t know what the cause is," Dr. Williams told me.

 

One possible contributing factor, Dr. Williams told me, may be in the type of ingredients used in the flavored primate biscuits or other foodstuffs the lemurs eat. The biscuits are primarily grain-based, she said, containing corn, soy, or wheat to provide one source of starch, soluble fiber, and insoluble fiber, along with protein sources.

Ideally, she said, a lemur's diet should consist of diverse types of fiber found in the same types of wild fruits and vegetables found on Madagascar. These could include several types of pectins, gums, and other fermentable fibers. Another area of concern may be omega-6 to omega-3 ratio of the lemurs' chow.

Education outreach and lemur nutrition research 

Dr. Williams 

A major challenge is in the need of further nutritional research in primates as a whole and, more specifically, with lemurs. Then, afterward, educational outreach.

After my interview with Dr. Williams, I contacted Michael Schlegel, Ph.D., director of nutritional services for the Zoological Society of San Diego to discuss her recommendations. Dr. Schlegel's role is to formulate meals for all the animals in at the San Diego Zoo and supervise how they are fed.

Dr. Schlegel found Dr. Williams's findings highly interesting, saying, "We're always looking for new research and we do balance diets so that fruit is only a component. They do get vegetables, but we know more is what's good for them."

Zoo keepers and zoo nutritionists like Dr. Schlegel rely on guidelines given by the National Research Council's Nutrient Requirements of Nonhuman Primates, much as Americans rely on Institute of Medicine for dietary guidelines.

"We look at publications, and adjust to individual needs. We try to base diets on animal energy and metabolic requirements," he said.

Schlegel agreed that current dietary requirements for all primates are based on limited studies. Further research is needed in areas such as analysis of dietary composition of wild diets as well as controlled trials with lemurs as a species.

As it stands, the science of nutrition and diet is still young for humans and lemurs alike, but so far the similarities on how the modern world affects human health and how captivity affects our far distant cousins are striking. 

Changes in genetic expression during weight loss and weight maintenance

by Amanda Jensen* 

Losing weight is an ambition with no end. To get fit, live longer, reduce injury, look better, feel better and sleep better will pave the road toward your skinny. Yes, losing weight is known to help the heart and boost insulin sensitivity, but the question still asked is: how?

There are differences between losing weight and keeping it off. From the Department of Clinical Sciences Malmo in Sweden, researchers found seven key genes expressed in adipose tissue (fat tissue) that change with weight loss and weight maintenance—a finding that brings science one step closer to understanding how the body responds to and regulates fat loss.

This randomized controlled trial shows that the genes expressed by adipose tissue change when an obese person trims down, and stays down. "For most people," the authors report, "maintaining a reduced weight is a difficult but important task to fully obtain the beneficial effects of weight loss."
Researchers placed 12 obese adults on a low-calorie diet for three months. After subjects lost 10 percent of their body weight, they embarked on a weight-maintenance program for an additional six months. The researchers took biopsies of adipose and blood samples at baseline, immediately following weight loss, and after the period of weight maintenance.

The participants had an average reduction of almost 19 percent of body weight, the researchers report. If trimming down wasn’t news enough, immediately following the weight-loss phase, insulin sensitivity and blood triglycerides improved. Improvements to HDL (the "good" cholesterol) were realized after weight loss had been sustained.

Gene Interactions

In total, the researchers reported 2,163 genes were affected during weight loss and 1,877 different genes were modified during weight maintenance. Two genes that were among the most strongly expressed, CETP and ABCG1, are likely responsible for the improvements to HDL observed after sustained weight loss. A high HDL gives the body has a greater capacity to clear cholesterol from the tissues and send it back to the liver to be recycled or excreted. Both genes code for enzymes that promote cholesterol transfer to HDL—lowering cholesterol is a way that weight loss may be effective for bolstering heart health.

Most dieters have found that the body really resists weight change. Researchers found that expression of the weight-guarding gene CIDEA was higher when the subjects were working to maintain their weight loss. In mice, blocking expression of CIDEA prevents weight gain during over-feeding. The increased expression of CIDEA in individuals trying to maintain weight loss supports the notion that the body defies shedding pounds by dropping metabolic rate.

A person carrying too much weight is also carrying too much stress for their body. Many of the problems linked with obesity occurs because the body to trying to cope. The researchers focused on two genes; MMP9 and TNMD, which were down-regulated as a result of weight loss and weight maintenance. MMP9 and TNMD are genes that may be responsible for adaptations in conditions like obesity and metabolic syndrome.

MMP9 codes for a matrix metallopeptidase. The structure of a cell is often referred to as a matrix, think of the scaffolding in building that can be moved, modified, or degraded. These metallopeptidases are the contractors for cells. Fewer MMPs means that fewer cells are broken down and fewer are built up. The result is perhaps more, but smaller fat cells.

TNMD codes for a protein tenomodulin: the contractor (or modulator) of the blood vessels. TNMD is higher in obese individuals and has been linked to fat mass as well as poor blood sugar control. The authors write that "taken together, low amounts of tenomodulin and matrix metallopeptidase 9 or related proteins may be important for the beneficial effects of weight loss."

Keeping the Weight Off

Adipose tissue, once thought to be a dormant receptacle of energy stores and an extra layer of insulation, is a metabolically active organ. Yes, fat cells do function and perform work. According to these researchers, they contain genes that affect immune response, hormonal balance, and even metabolism—all involved in creating a "set point" for weight.

Weight loss is no easy feat, especially when the body finds security in fat. Losing weight can feel like an uphill battle, the yo-yo dieting, and perpetual cycles of weight loss and weight gain do not do anyone any favors. With weight loss the body begins to fight for its fat stores; hormones change, satiety is impaired, and metabolic rate shifts. This resilience, according to researchers, is largely a product of the genes being expressed.

"Future research on the beneficial effect of weight loss should focus on long-term effects assessed after a period of weight stability" recommend the researchers. These results provide exciting insights into the physiology of fat and its genetic adaptations. Anyone can lose weight but, according to the authors, sustaining it is the true battle with true benefit.

Reference

Johansson, L., Danielsson, A., Parikh, H., Klintenberg, M., Norstrom, F., Groop, L., & Ridderstrale, M. (2012). Differential gene expression in adipose tissue from obese human subjects during weight loss and weight maintenance American Journal of Clinical Nutrition DOI: 10.3945/ajcn.111.020578

*Introducing the wicked-smart Amanda Jensen, in her first guest appearance on the Evolving Health blog. She enjoys science, writing, Indian food, traveling to all sorts of places, and playing tennis. She's also a good friend to have in case you're ever in need of in-depth conversation about lipid metabolism. She's also a recent graduate of Arizona State University's nutrition program. Congrats!

Why a fat brain made us more vulnerable to heart disease

Natural selection granted us large brains. The evolutionary cost is having to feed them. The human brain's high-energy demands led to development of a strong preference for fat. We consume more fat than any other primate on average. We are also adapted to more easily digest and metabolize fats.

There are two major kinds of fat that our brains depend on most for its development and regular maintenance. These are the long-chain polyunsaturated fatty acids (LC-PUFAs), omega-3 docosahexaenoic acid (DHA) and omega-6 arachidonic (AA). These two LC-PUFAs can't be made de novo, making them essential in the diet. DHA and AA are supplied by seafood, eggs, or animals. They can also be supplied as their 18-carbon precursors alpha-linolenic acid (ALA) and linoleic acid (LA), found mainly in plants and their seeds.

ALA and LA precursors require conversion to become long-chained through a series of steps of desaturation and elongation. In particular, delta-5 and delta-6 fatty acid desaturases build onto the carboxyl end of the carbon chains of the ALA and LA by introducing double bonds. These converting enzymes are rate-limiting.

The rate-limiting enzymes are encoded into the genome by FADS1 and FADS2. The FADS region has been of special interest to researchers because of variations in single-nucleotide polymorphisms (SNPs) that could lend clues about human evolution including our larger brains. Yet, to date, there have not existed any studies evaluating FADS mutations among humans and related species.

Now, researchers from Uppsala University, in Sweden, along with scientists at MIT, Harvard, and major European Universities, have found genetic variation in the FADS region in present-day humans that made them uniquely adapted to biosynthesize DHA and AA. The same adaptations could also help explain why some ethnicities have a higher susceptibility to chronic disease today.

The international team set out to investigate by using genomic data from contemporary human populations, archaic hominins, and more distant primates. They used SNP genotype data from more than 5,600 individuals across five European population cohorts. They evaluated mutations in the FADS region that are strongly associated with omega-3 and omega-6 fats.

Two common FADS haplotypes

Among present-day humans, they report, exist two common FADS haplotypes, or groups of alleles defined across a set of 28 SNPs, that are "dramatically different in their efficiency" to biosynthesize DHA and AA from he shorter ALA and LA.

The 28 SNPs of two main haplotypes (A in red, D in blue) and nucleotides of species.

Haplotype A, limited in conversion efficiency, appeared nearly 606 thousand years ago. Rhesus monkeys, chimpanzees, gorillas, and Denisovans all bear haplotypes "very similar" to haplotype A. Neandertals too, although based on incomplete sequences, have similar haplotypes to haplotype A.

Haplotype D, having greater conversion efficiency, appeared somewhere between the lineage split with Neandertals. That was around 500 thousand years ago and before the exodus from Africa some 50 to 100 thousand years ago. Both haplotypes must've been present during the exodus or else we wouldn't see the existence of them in modern humans today.

The researchers speculate that "a very rapid increase in brain size of hominoids" probably involved selection and the increased frequency of haplotype D. That does not mean that haplotype D had any direct effect on brain size, but that it was highly advantageous in environments where there was limited access to AA and DHA to feed the brain.

Haplotypes A and D in Present-day Humans

Nowadays, the researchers found, nearly all individuals of African descent had haplotype D. The high frequency indicates positive selection for the haplotype with more efficient conversion in the face of limited availability of LC-PUFAs in early Africa.

On the other hand, nearly all Native Americans had haplotype A. The reason, the researchers propose, may be because of a "bottleneck effect in the colonization of the American continent, possibly in combination with relaxation of the selective pressure as a result of a diet higher in essential LC-PUFAs."

The data are mixed in those descended from Europe, Oceania, East Asia, who are reported to have haplotype D at a greater frequency.

The frequencies of A (blue), D (red), and mixed (gray) haplotypes.

Health Implications


How can the knowledge of these haplotypes inform guidance on diet? The differences in haplotypes may explain why individuals of specific ethnicities may be more susceptible to chronic disease compared to others.

Individuals with haplotype D biosynthesize more AA and DHA than individuals with haplotype A. While this adaptation may have been useful on the African savannah, the researchers propose it has drawbacks as a "thrifty genotype" in our modern world. As plentiful as LA (from corn and soy) is in the Western diet, haplotype D may lead to higher levels of AA-derived pro-inflammatory eicosanoids, which raise the risk of atherosclerosis and coronary artery disease.

A different set of problems are presented for individuals with haplotype A. These individuals may be protected against a high-LA diet to a degree because of limited conversion to AA. However, they are more dependent on animal foods for adequate amounts of DHA due to inability to convert sufficient ALA to the longer-chained counterpart on a more plant-based diet.

The researchers propose, "FADS genotyping should be included as a diagnostic for dietary recommendations."

As genetic testing is not yet widely available, here's a more viable solution for the sake of a large human brain and a genome not well adapted to a high-LA diet: eat less LA; and, eat more foods enriched in long-chained omega-3s such as eggs, grass-fed animals, and seafood.

Reference

Ameur et. al. Genetic Adaptation of Fatty-Acid Metabolism: A Human-Specific Haplotype Increasing the Biosynthesis of Long-Chain Omega-3 and Omega-6 Fatty Acids. American Journal of Human Genetics, April 12, 2012 DOI: 10.1016/j.ajhg.2012.03.014

Related Posts

• Omega-3 Overview and Book Review of "Queen of Fats" by Susan Allport
• Boost omega-3 by reducing omega-6
• How diet shaped human evolution

Lindeberg: Focus on Food Choices, Bioactives, not Nutritionism

Dr. Lindeberg weighing a Kitavan man. 

While training in family medicine, Staffan Lindeberg, M.D., Ph.D., read a paper (published in 1985) in the New England Journal of Medicine that would alter the course of his future research. It was entitled "Paleolithic Nutrition" and one of the authors was Boyd Eaton, M.D.

It was about the same time Dr. Lindeberg had heard from a neighbor that humans had the guts of vegetarian -- to which he responded, "Oh yeah?" His neighbor was  influenced by one of a number of nutrition "stories," as Dr. Lindberg calls them, and not based on actual scientific investigation.

"People like John Harvey Kellog [inventor of corn flakes and strong proponent of a vegetarian diet] has had more influence on thinking about a healthy diet than Darwin has," Dr. Lindeberg says.

So began his journey to discover more about evolutionary biology's connections to human health, diet and Western-style chronic diseases. Twenty-six years later, last weekend on Aug. 5 in Los Angeles, Dr. Lindeberg presented alongside Dr. Eaton and several other proponents of a  "Paleo-style diet".

However, unlike most of the other presenters, Dr. Lindeberg clarified he doesn't necessarily recommend a diet containing high amounts of meat (rich in protein and fat) along with little to no carbohydrates. Instead, he said that based on his research he's convinced that the main difference from a Western-style, modern diet and that which hunter-gatherers eat is the concentration of bioactives. These bioactives, he explains, must be the real basis by which ancient diets protect from disease.

The alternative hypothesis of several researchers is that the chronic habit of postprandial (after meal) increase in glucose leads to Western disease. It's not proven, Dr. Lindeberg says, and because so current nutritional advice rests mainly on epidemiological studies.

"It's difficult to make clinical trials, to have two groups eat what they think is the same type of hamburger. One group eats hamburger with real meat, one group eats placebo meat. Of course it's impossible to do it. Maybe some time in the future," Dr. Lindeberg said.

So, lacking randomized clinical trials, it's important to begin thinking evolutionarily. That's not to say that whatever is natural is good for you. This is "nature romanticism," Dr. Lindeberg warns. For example, it is wrong to think that soy formula because it is "natural" is as healthy as breast milk. After all, a lot of these plants evolve their own defense system deliberately to target we herbivores.

Closely attached to developing a hypothesis based on evolutionary terms, is observations from hunter-gatherers. When Dr. Lindeberg studied the Kitava of New Guinea, in 1990, they chose that particular population because they had enough ethnic people and large enough population to obtain data.

Unlike other hunter-gatherers like the Inuit of Greenland that eat a low-carb diet or the Ache of Paraguay, the Kitavans are more easily described as "primitive horticulturalists." They eat plenty of yams, sweet potatoes, fruits, and coconut. They eat pork meat only on occasion. Yet, despite their diet, as a population they enjoy relatively little incidence of myocardial infarctions, stroke, and atherosclerosis.


Dr. Lindeberg dismissed criticism that he may have made a mistake in his observations and that the Kitavans were eating more pork than reported in his data. "These people are in love with the low-carb hypothesis," he said.

His findings are consistent with those from East Africa in 1920s, where stroke was absent among the population, but then it became the most common neurological disease. History repeated itself in Papua New Guinea.

Any traditional population that migrates to a Westernized diet develops high incidence of hypertension and stroke including those where the so-called  Mediterranean diet is widely eaten have a high incidence of stroke. So, in comparison to a the paleo concept, it's logical to accept it as a better diet. However, Dr. Lindeberg says, our "logic is not working."

Kitavan girl

But, what it is it about the diets of the developed world that contribute to disease? Is it carbs? No, because Kitavans can live to a ripe old age -- even some reaching centenarian status -- lacking any Western diseases while on a high-carb diet. Is it exercise? No, Kitavans are active but not anymore than an average construction worker in Sweden, Dr. Lindeberg said.

"I don't think you need to eat a low-fat diet. I think you need to stay away from Western food."

Again, Dr. Lindeberg stresses the need to stop talking about calories, carbs, and fats as "big villans" and begin focusing on bioactives. Initial controlled trials he has led that investigate the effects on a "paleo diet" rich in lean meats, fruits and vegetables have led to intriguing results.

"We've found with early diabetes or impaired glucose intolerance (pre-diabetes) all of them reverted to improved glucose tolerance," he said.

There are other benefits from eating similar to the way our hunter-gatherer ancestors did. He notes that by eating only paleo food, most people find they automatically achieve calorie restriction. Eating less is also better for the planet.

And paleo is not too far off from conventional nutritional advice. If you look at a DASH (Dietary Approaches to Stopping Hypertension) eating plan -- which is rich in lean meats, low-fat dairy products, whole grains, and fruits and vegetables -- Lindeberg says, "it's more or less paleo." (I was glad to hear that since I've been recommending the DASH eating plan for years to everybody.)

Dr. Lindeberg clarifies that what he thinks the problems lie is in focusing on fats, carbohydrates and calories instead of food choices.

"I think nutritionism [a term coined by Gyorgy Scrinis and popularized by author Michael Pollan] has been too much on the agenda," Dr. Lindeberg said.

To read more about Staffan Lindeberg and for photo credits, see  http://www.staffanlindeberg.com/KitavaPhotos.html

Wake up, Neo-evolution

What would you change about your own naturally evolved, naturally flawed body? Would you choose genetics to avoid diseases like Alzheimer's, diabetes, and cancer? Would you enhance your brain to increase memory and to boost creativity? Would you choose more fast-twitch muscle fibers to run faster or longer? Would you live longer?

These are the questions that Harvey Fineberg, president of the Institute of Medicine, discusses in this new TED talk given in March that was posted only this month. Fineberg says that a new era of neo-evolution -- in which we, as humans, could guide the selection of traits that would define the course of humanity -- is upon us, and he called it "exciting," but "frightening."

I want to answer all of his questions with a "Yes, sign me up!" Who is insane enough to reject a world with an absence of disease, of aging, of dying and death?

Apparently, there are quite a few people. Hava Tirosh-Samuelson, professor of history at Arizona State University, is one of them. Earlier this month, at ASU's Origins Project Science and Culture Festival Tirosh-Samuelson was speaking about a completely different topic when she suddenly surprised us with a few critical words of the "so-called trans-humanist movement."

In a nutshell, her argument is that we still haven't a clue of what humanity is to begin with, so reason suggests against trying to define what it should be in the future. Naturally, after her talk, I decided to ask Tirosh-Samuelson a few questions about her views.


In my discussion with her, she conceded that eliminating suffering from disease was a good thing in its own right and also agreed that because of medicine and technology all of us are already trans-humanists in a sense. So, why the hostility toward neo-evolution, trans-humanism, the singularity?

She told me that a trans-humanist future -- in which everyone has enhanced faculties, superior brains, superior fitness, etc. -- has the grand possibility of ending up very boring.

After all, she said, "What defines happiness? We don't know. What defines humanity?"

You can see her essay on the subject here.

While discussing with Tirosh-Samuelson about these questions, I was reminded of several sci-fi movies including Gattaca and The Matrix (I can now think of at least a half dozen others now), where we're presented to two completely different stories of the human condition in a futuristic world governed by technological advances. In each, our hero defies imposed order and seeks to achieve his greatest potential.

Maybe, just maybe, that is what happiness is -- seeking your own greatest potential. Or, maybe, happiness is simply in the journey. Either way, I'm inclined to suggest that we find happiness by heeding to the words of Joseph Campbell: "Follow your bliss."

And as for Fineberg and his neo-evolution and what it will mean to the future of humanity, we can all agree that it's just going to happen anyway -- so why be frightened? why not welcome it? why not just wake up to its possibilities? -- because what is really happening is humanity itself on its never-ending journey seeking survival, enhancement and comfort of itself, and happiness (whatever that is).

Pornography in the Primordial Soup

Panel of scientists debate on "What is Life?"

Sometime between 4 and 3.5 billion years ago, the emergence of life had intense beginnings on a young planet in the midst of a so-called primordial soup—consisting of water vapor, carbon monoxide, carbon dioxide, nitrogen, and ammonia and shaped by strong winds, electrical storms, volcanic eruptions, and ultraviolet radiation.

In 1953, Stanley Miller and Harold Urey put Earth's primitive conditions to test for the first time in a famous laboratory experiment. It yielded variety of amino acids and organic compounds. The researchers realized something more: that no early form of life could have ever survived the world of today, because of the presence of oxygen that directly attacks at the bonds that holds together complex molecules.

Scientists also now know that the original blueprint of life was not DNA, but short RNA strands that may have also served as their own biological catalysts, before enzymes ever evolved, providing for self-replication. This early RNA world would eventually give rise to DNA, which used RNA as its template for encoding the genetic information to build proteins.

Still, there are several other questions that remain surrounding life's origins such as How can life be defined? Where did it happen? What came first: replication or metabolism? Could life have happened elsewhere in the universe? What would an alternative form of life and biochemistry look like?

Last weekend, to discuss the questions, a small panel of six scientists gathered at workshop at Arizona State University with a major goal of charting out the steps between the RNA world and greater complexity. Some would say theirs was a hopeless cause and a waste of time.

Then, on Saturday, February 12, a public debate  took place between them with an overarching theme entitled, "What is Life?" Theoretical physicist and cosmologist Lawrence Krauss, ASU professor and director of ASU's Origins Project defended the exercise as uniquely human.

"It's a profound and deep question that hits at everything we think about," Krauss said, noting how the question has a powerful draw. "It sounds like a simple question, the answer isn't so simple. In fact, every time I think about that question, I think about pornography."

He referred to a 1964 Supreme Court case where Justice Potter Stewart once was asked to explain the definition obscene pornography. "I know it when I see it," the judge responded. Krauss said, "In some sense, life is like that."  

Life: Complexity with a Specified Direction

Evolutionary biologist Richard Dawkins further  elucidated the significance of the question in characteristic eloquence, "This may be the only planet in the universe that contains eyes to see it, brains to think about it, and wonder about it. I don't believe that. I suspect there is plenty of life in the universe, but this is the only kind of life we know about."

According to Dawkins, because the laws of physics apply all over the universe, it is likely that life could have materialized many times by the process of evolution by natural selection. Life, then, would have to be defined as anything that is highly statistically improbable, but that appears to have a specified direction.

"You have to add that 'specified direction' because with hindsight you could say any old heap of rubbish is statistically improbable in that there has never been a heap of rubbish exactly the same," Dawkins said. "What's special about life is that living things are statistically improbable in a direction, which you could have specified in advance. It's not always exactly the same, but birds are good at flying, fish are good at swimming, moles are good at digging. All living thins are good at something, whereas lumps of rock aren't.    

Whatever life is, it is characterized by its complex molecules that must somehow create the energy to convert raw material into a structure, all while excluding anything that may be toxic to those reactions of metabolism and reproduction. This is why geneticist and Nobel Laureate Lee Hartwell argued, "Inevitably, life will be cellular. Cells will have been selected to have an optimum size and optimum structure for whatever lifestyle they happen to have."

Searching for a Second Genesis

A sort of definition of what to look for was heartening for NASA planetary scientist Chris McKay, "What Lee said was a beautiful synthesis of how we can search for life, and I want to take that to the specifics of how do we do it in near tem missions in our solar system."

There is an advantage to finding other forms of life in our own solar system, argued McKay, because "then we'd know that life is common in the universe." The task of finding other forms of life in the solar system, even on our own planet, is one promoted by cosmologist and astrobiologist Paul Davies.

Davies doesn't see things quite the same way as McKay. "How can we find this second sample of life? Chris has said one way you can do that is you can go somewhere else in the solar system and find it there. That's great. But it's also very expensive. Is there another way? Well, no planet is more Earth-like than Earth itself. Shouldn't it have occurred many times right here on our home planet? How do we know it didn't?"

While Davies looks for alternative life on Earth—a process that he boldly claims can be completed in less than a decade—biologist and entrepreneur Craig Venter is more interested in creating synthetic life.

Venter explained how he and his colleagues synthesized DNA and chromosomes and inject it into E. coli, which he likened to creating a computer program that builds its own computer, or as he puts it, "A situation where the software actually leads to building its own hardware, but we're trying to go much further. We had to learn how to boot up this bacterial genome."

Change the DNA, change the software, and you change the species, Venter explained, and as others have pointed out, his team did use a living cell, but the cell was the first one to ever have synthetic DNA.

Living Artificial Intelligence

Among these scientists, one thing was certain: the definition of life could not be agreed upon in the face of alternative forms of life in the universe, in our own solar system, on the Earth, or from creating life from scratch. But, perhaps, a definition of life isn't needed after all because, as Krauss put it, anyway, it could change.

"Let me throw it in a completely different direction," Krauss offered in the debate."When computers become conscious, which they will—my Mac is far closer than the PC—will we call them life? And they'll object if we don't, I suspect. I think the definition is a moving target."

After all, the difference from what Venter is accomplishing—with software that makes its own hardware—and computers is that computers simply haven't done that yet (made their own hardware), but when they do, which will happen in at least one or two decades, Krauss said, "they will become the dominant forms of intelligent life on the planet and biology will have to incorporate that in order to keep up."

At the end of the debate, the inevitability of life in the universe was the lesson really learned, given that there could be life lurking almost anywhere.

Be it in a biological world, a  synthetic world, or another kind, life can defined as simply… we'll just know it when we see it.


To read more about the entire weekend conference on origins of life, see Dennis Overbye's article in the New York Times.

UPDATE: the science network has now published the video of this debate. Click on the video to watch below.

Evolution of Lactose Tolerance in Africa

Sarah Tishkoff

Most African populations have lactose intolerance, but as recently as 3 kya a few pastoral populations have gained the ability to digest milk, which provides evidence of yet another example of ongoing evolution in human population since the time of their origins.

Sarah Tishkoff has been studying this phenomenon of recent lactose tolerance in African pastoralist populations. She shared her findings on Sunday morning at #AAASmtg in Washington DC.

The ability to digest milk as infants is with the expression of lactase-phlorizine hydrolase (lactase), which is specifically expressed by brushborder cells in the small intestine.

But shortly after weaning, the expression of lactase decreases sharply -- that is, except in populations that are lactase persistent. In 2002, an elegant genetic study found the gene for lactase in European populations.

Tishkoff showed us in charts and on a map how she performed genetic studies on the African pastoralist populations with lactase tolerance. Based on the findings, she found a perfect example of convergent evolution -- that several of the populations had developed lactose tolerance in different ways genetically -- because of strong selective pressures to drink milk.

With her latest study and archeological data, she is now tracking the origins of pastoralism. She showed us a map (Smith 1992) where it's clear that most lactose tolerance emerged only in the last few thousand years, but at different times. Her research confirms that pastoralism was brought into southern Africa only recently, most likely from the Great Lakes region.

"So, are humans still evolving? Yes," Tishkoff said.

Why was milk selective pressure so strong? There has been a lot of debate, Tishkoff said, such as whether it is the source of water, protein, or calcium. But it's not everywhere, so there has to have been a cultural transformation in each region.

"There's only some environments that can handle that cultural development," Tishkoff said, but in each case, there has to be an underlying genetic variation and the different variants suggest that perhaps for some populations had a more difficult time with the change or took longer to adapt to it than others.

Designing biology

Photo credit: Sara Fulcher on Flickr

Where can we find a cure for cancer, new semiconductor technology, or the solution for turning waste plant materials into biofuels? The answer is enzymes that are produced through "directed evolution," according to Frances H. Arnold, professor of chemical engineering and biochemistry at the California Institute of Technology.

Arnold's lab doesn't synthesize enzymes as other labs do. She and her team "evolve them" toward a certain desired goal in the same way that nature has done it for 3.5 billion years.

Aronold presented an overview of her budding field of work to an audience at American Association for the Advancement of Science annual meeting (#AAASmtg) in Washington DC. The field of directed evolution is relatively new and includes few people at the present time, but Arnold sees high hopes for the future.

"When I started engineering proteins a long time ago, there appeared to me an algorithm that dos a really good job and that's evolution," she said. "Evolution works because the regions that life has discovered and explored are rich in function. Directed evolution exploits smooth paths in the fitness landscape."

The fact is, DNA is cheap and easy. Designing it isn't.

"We're getting really good at making DNA. The price is dropping every day," Arnold said. "But we don't know what to write. We can synthesize any sequence. We can insert new code (referring to Craig Venter's recent success), but we don't know how to write it. We don't even know how to write a single protein."

And, when it comes to enzymes for use inside a complex biological system, she says,"Details matter. We don't understand the details."

Freed from constraints of worrying about biological function, directed enzyme evolution allows Arnold's team to explore new pathways and possibilities.

Arnold presented a few of her enzymes that have been created through directed evolution. Her source materials are from every possible place -- the "heel of your shoe," for example -- and she doesn't limit herself to what's available.

Frances Arnold

By combining several different enzymes and selecting for specific active sites, she can produce more stable proteins that perform practical work.

Where is directed enzyme evolution going in the future? Arnold says that functional protein can be used in several ways. One example Arnold gives is in materials chemistry, such as the work of Angela Belcher of MIT, who uses virus proteins to enrobe minerals onto protein coats.

"You can make a virus that really loves to bind to a single-walled carbon nanogen," Arnold said, which would be a boon for semiconductor technology.

There is really no end to the influence that directed enzyme evolution could have on the world, from highly specific targeting in biological systems to technology.

In short, there's no doubt of an exciting future in intelligently designing new biology.

How environmental change shaped human evolution

Anna Di Rienzo

Humans originated in Africa and then dispersed all over the world to environments that differ in terms of climate, biodiversity, etc, which has brought selective pressures on different populations. At #AAASmtg in Washington DC on Saturday, Anna Di Rienzo presented her research on the how this dispersal has left signatures of adaptation to the pressures. Here are my notes from the talk.

The "Out of Africa" theory has it that humans left Africa 50 Kya and then Neolithic revolution happened 14 Kya. They shifted away from foraging subsistence to horticulture. We also know that levels of human skin pigmentation changed with latitude of populations. In addition, body size and proportions changed. For example, Inuit have quite different proportions for the cold North.

Metabolic traits differ across human populations also, causing disease related traits to occur such as high blood pressure, high triglycerides, or high cholesterol. A prominent example is the rising prevalence of type 2 diabetes. "It's been long proposed that it’s a [genetic] susceptibility to change in lifestyle and diet," Di Rienzo said.

There is a prevalence of inter-ethnic differences in disease and traits. Environmental risk factors clearly play a role in shaping differences. There is a growing conseus that genetic factors also contribute. Is there evidence for genetic – in addition to cultural and physiological – adaptations? How much of the phenotypic diversity is adaptive? What is the contribution of local adaptive traits?

These question led to many studies on signals based on haplotype structure such as lactase persistence, which is common in Europe and in agropastoralist populations, but rare elsewhere. The ability to digest milk in adult life became advantages with the introduction of animal farming, Di Rienzo said. Another example is the FY allele that is fixed in most sub-saharan Africa and is virtually absent everywhere else. FY codes for a chemokine receptor (antimalarial).

Selection for polygenic traits is expected to generate subtle changes in allele frequency at multiple loci. Standard approaches are unlikely to capture these signals. The signature of selection is for monogenic (small shifts) versus polygenic traits.

Her approach is for search of information about environmental selective pressures. She searches for correlations between alledle frequency and environmental variables. She takes into account the geographic structure of human populations shaping distribution.

She used a large dataset of more than 642,000 autosomal SNPs. Environmental variables included climate, ecoregion, and subsistence. Climate includes seasons, ecoregion with temperature, humidity. The genome-wide evidence for environmental adaptations is that most of the genome doesn’t contain genes or variants that affect the function of the genes.

Natural selection acts only on variants that have both functional and phenotypic effects. Is there an excess of test SNPs relative to control SNPs among those with lowest minimum p-values?

The test SNPs used are enriched for SNPs with functional effects. Control SNPs are unlikely to have functional effects (e.g. far from genes).

In all cases, a significant excess of the test relative to control SNPs indicating that environmentals select pressures shaped the geographic distribution of variation in the human genome.

The results suggested genome-wide evidence for environmental adaptations,” Di Rienzo said.

Pancreatic lipase-related protein 2 hydrolyzes galactolipids, is the main component in plants. The truncated PLRP2 protein, which occurs at a higher frequency in those populations with higher consumption of cereal grains. PLRP2 is associated with cereal rich diet.

Two examples of patterns at individual SNPs are “foraging” and “nonforaging” and she shows a slide with patterns showing differences in Africa, Europe and other. In each geographic location, there is a shift in allele frequency that allude to differences in diet of the populations.

The shift in allele frequency is not dramatic, but small. The top signals are with categorical variables like roots & tubers, foraging, polar ecoregion, and a dry ecoregion. Top climate variables have to do with seasons.

“Selection doesn’t act on genes, it acts on phenotypes. The phenotypes are enriched with signals for environmental correlations,” Di Rienzo said.

Disease classes are influenced by environmental selective pressures. Climate influenced cancer, CVD, immune, infection. Subsistence influenced metabolic and reproduction phenotypes. 

The overlaying signals of environmental correlations and genome-wide association studies show this flow:

SNP is affected by environmental correlations and GWAS, then selective pressures produce phenotype. It’s also known that pathogen diversity follows a gradient on climate factors, which can affect immune, autoimmune adaptations.

Di Rienzo made these conclusions from the data:

- Strong GWAS to climate, ecoregion and subsistence

- Signal of adaptation to environmental pressures are subtle, but consistent shifts in allele frequency

- Adaptation to local environ and common disease may have similar gene architecture

- Signals of climate correlations make a contribution to diseases of immune response and pigmentation traits

More information can be found at dbCLINE

http://geneapps2.uchicago.edu/dbcline/main.jsp  

How diet shaped human evolution

Anyone who is keenly interested in having a better understanding of why we eat what we eat as human beings should take an hour or so to watch this introductory talk given by anthropologist Teresa Steele, of UC Davis, given at the California Academy of Sciences on the topic of evolution of the human diet.

I found her talk fascinating, especially because I've been highly interested in how the use of fire and aquatic animals may have played a part in fueling human brain growth, so I ended up taking copious notes. I should note that there isn't anything new presented here, but Steele is excellent at presenting the chronology. If you don't have an hour to watch, then just see my notes below chapter by chapter from "Australopithecus to agriculture."

Human diet is unique among apes

Steele finds that diet is central to her research. "If we want to live, we have to eat," she says. Food is what ultimately supports demographic populations. One thing that is unique about humans in comparison to other apes is a long childhood, a long learning period, that is required for acquiring the knowledge necessary to become successful foragers in a wide environment. After all, humans have exploited almost every nutrient resource in their short time on the Earth.

Another unique thing is how much meat we consume. A large portion of our calories comes from meat. Unlike chimpanzees, who eat the most meat among apes, human eat about 10 times more, Steele said. And we eat animals that are usually larger than us like wildebeasts, reindeer, and mammoths. Steele shows a graph comparing chimp diets to that of tropical hunter gatherers groups, who typically eat little meat. Other hunter-gatherers of the North like the Inuit eat a diet almost entirely of meat. In general, humans specialize in acquiring nutrient-dense foods meats, tubers, and nuts, while chimps select non-nutrient dense like leaves that are more easily collected.

Research themes

When did these differences evolve? Steele presents us with her research themes, which include the following:

• Meat eating. We are consuming animals that are larger than ourselves like wildebeast, reindeer, horses, and so on. Chimpanzees hunt for colobus monkeys, birds, and small amphibians. So when did meat eating appear and when did the transition occur to eating animals larger than us?
• Hunting technology. What technology did humans use to acquire large animals? Spears, bows and arrows, projectile technology? These are complex, so they can represent greater cognition. When did they occur?
• Intensification of resource use, including agriculture. This happened much more recently.

Methods of Study

What methods does Steele use to construct ancient human diets? She says that zooarchaeology and tool analyses gives us a window into ancient demographies. There are stone, bone and antler tools. And, on occasion, organic wood and plant tools are preserved. Also, biological anthropology helps tell us more such as skeletal morphology and bone chemistry.

Lucy's diet

Steele introduces the diet of Lucy's species first, Austrolopithecus afarensis of 3.7-2.8 mya, who ate a flexible diet suitable for a variety of habitats.

The skeletal biomechanics and dental structure suggest they ate mostly soft fruits and occasional hard seeds. However, Steele says we assume that they may have eaten some meat because chimps eat meat, but it's unclear just how much.

She points out that, recently, there was a groundbreaking discovery published in Nature (and reported in Scientific American by the science writer Kate Wong (Twitter: @katewong) ) of cut-marked bones in Dikika, Ethiopia suggesting Lucy's species even used stone tools for eating meat.

"This has opened up a window," Steele says for more research, especially in the possibility of stone tool use for extracting nutrients from carcasses of smaller animals. It's worth noting that no stone artifacts were found associated with the cut-marked bones (paleoanthropologist John Hawks (Twitter: @johnhawks) has written more about this topic on his blog).

Cut-marked bones 2.5 million years ago

Typically, a discussion of human diet begins at about 2.5 mya when there is an abundance of cut-marked bones (such as the jaw of a wildebeest) and percussion marks from marrow extraction. Marrow has been an important human resource for nutrients up until modern times because it's high in fat, high in calories.

There is also evidence of Oldowan artifacts (hominin stone tools) available so we know what they were using to get to the marrow.

Then, at about 1.8 mya there are a lot more assemblages, more stone tools, as found in Olduvai Gorge, Tanzania, by Mary Leaky. There are also lots of large bodies bovids and carnivores on the landscape. Steele asks, How did these ancient hominids acquire these large carcasses? Is it conceivable that they could've brought down a wildebeast with just tools?

This is where we get into a discussion of scavenging versus hunting, she said. A related discussion is what percentage of the diet was meat-based versus plant-based. Also, were these ancient hominins practicing passive scavenging getting to a carcass to get the last scraps of meat or breaking open bones for marrow. Or was it active scavenging, chasing off carnivores?

These are all active areas of research. For answers, researchers look in locations of lakeside margins. Bovids came to drink, carnivores know this, we look into these locations to try and reconstruct the foraging.

Aquatic animals

Published recently in the springtime, was a paper suggesting that 1.9 mya in East Turkana, there's evidence of Oldowan foraging of carcasses of aquatic animals like crocodiles and turtles. Steele shows a cut marks on a toe bone of a croc, turtle shells and catfish bones.

"For the first time, we see exploitation of aquatic resources highlighting the diversity of diet. Hominins are very opportunistic, exploiting whatever was available," Steele said.

"This also raises a challenge as with cut-marked bones with Dekika, to try to see if there are cut-marks on similar bones," Steele explains. "The small animal component has been overlooked so we may need to look closer."

Steele also discusses another interesting aspect of using aquatic resources (which will interest any nutritionist like myself). The aquatic resources would have been an easier way to access long-chain omega-3 fatty acids, which are also present in organ meats and brain tissues of large animals.

"The long-chain unsaturated fatty acids are needed for brain growth," she explained. "At this time period we do see an expansion of brain sizes, so perhaps there's a relationship here. We need more data, more examples where we see brain expansion with this kind of diet."

Archeulean hunting and scavenging

Moving more recently in time, we see Homo erectus, hominins of larger body size, and who were first to populate Eurasia 1.6 mya to 285 kya. Were they hunting or actively scavenging? This is unclear, but earlier in Archeulan, we see evolution of technology.

Tear-drop shaped hand axes appear and body size changes. The humans are obviously living in social groups. An illustration she uses takes the liberty of showing piles of plant remains used to make wooden spears. The plant use is unknown.

There are a large number of animal bones with few cut marks. So, the question remains, were hominins still minor players as carnivores, simply cutting off limbs and eating elsewhere. The challenge is finding places away from water sites such as in caves.

Also, we start asking questions about use of fire at this time period.

Wood spears

At around 400 kya, Steele shares that there are one or two examples of exceptional preservation of organic materials such as wooden spears (survived in an oxygen-poor environments from marshes of Germany). They are more likely to be thrusting spears. They have been fire-hardened, sharpened, so it indicates use of fire.

Fire is really useful for warmth, protection from predators, for cooking and cooking really changes the nature of food. It helps make inedible foods edible, releases nutrients for our digestive systems. But fire doesn't preserve well.

The earliest known site where fire is documented is in Israel, dated to 780 kya. "We have an indicator of fire use and plant remains. They're preserve better once charred in archaeological sites," Steele says. "We don't find it common until about 300,000 years ago." This is between Oldowan and modern behavior in the Archeulian.

Neandertals

About 200 kya came the Neandertals and they were competent hunters and manufacturers of stone tools. Interestingly, despite these complex behaviors, they did not have as long a childhood. The Neandertals were able to pick up their abilities pretty early in life.

As part of her post-doc in Germany at Max Plank Institute, Steele worked with identifying species in archaeological sites where Neandertals hunted reindeer and bison. She showed antlers, elbows of reindeer fractured for extracting marrow, and examples of bones in discard piles due to little meat.

"We also see very little carnivore involvement and abundant human impacts, unlike the earlier where there was very heavy carnivore involvement meaning humans were hunting," she said. The Neandertals were dominant carnivores by this time.

Now we can ask about hunting strategy. Steele explains she uses a very low tech method: "We have a number of mandibles, so just looking at the eruption of teeth, we can reconstruct ages of animals." Also, reindeer are conveniently sexually dimorphic and because reindeer give birth at a moment in spring (babies are born at once) we can look at eruption of teeth to see if they're hunted. In a specific location, all ages are present, males and females, so it looks like the reindeer herd would have been slowed allowing the humans to hunt more of them.

Bone chemistry

Carbon isotopes tell us about the vegetation in the environment and nitrogen isotopes tell us about the trophic levels. Carnivores have more concentration of nitrogen. Animals that are aquatic even more nitrogen, so we can look at bone chemistry to reconstruct diet. There aren't much indicators of plant remains, but in a Neandertal tooth you see it's heavily etched by roots because of the acid of roots. The bone chemistry data put Neandertals right along the lines of other carnivores. The majority of protein came from meat (although not mentioned in the talk, new findings show they also practiced cannibalism, reported via science writer Carl Zimmer (Twitter: @carlzimmer)).

Hunting technology

How were the Neandertals doing the hunting? It appears they were using thrusting spears. We know this because it's possible to look at stone artifacts to see if they are aerodynamic or more asymetrical and lumpy for a thrusting spear. We can look at the breakage of the tip as well as the butt. In characteristic way we can look at the breakage.

Middle stone age in Africa 285,000

So while Neandertals are doing their thing in Europe, what's going on in Africa? In Africa, we have the middle stone age and humans who were morphologically similar to us. The big discussion in paleoanthropology is, How modern were they? Did they have symbolism? Were they just like us or behave more like Neandertals without as much symbolism?

In the middle stone age we have good evidence of hunting and burning. There was abundant burning. But, within the middle stone age, we see no evidence of consumption of fish. The people seem to be limited in capturing fish and birds, although there were people accessing coastal resources along the southern coast of Africa, eating a number of mollusks. Could mollusks have fueled brain growth and brought with it symbolic behavior? There were also a number of fireplaces. Did fire fuel brain growth (if you ask primatologist Richard Wrangham as I did last February, then the answer is a resounding "yes!")? This is something that requires further research.

Modern humans in Europe

In Europe about 40 to 10 kya, we have Upper Paleolithic with fully modern humans in Europe. They hunted large game similar to Neandertals and with projectile technology unlike Neandertals. People who were just like us in biology and behavior. This is when we see projectiles for the first time. We see the reconstruction of a spear thrower, with an adle addle.

These modern humans then also enjoyed a diverse diet with abundant small game like fish and flying birds. That's quite different than what their Neandertals cousins were doing, and what humans in Africa of the middle-stone age were doing.

We can also see this in the bone chemistry of the Upper Paleolithic humans. There was definitely protein coming in from aquatic sources, per the nitrogen values in the bones. It's also clear from the bone chemistry that modern humans were eating a much more diverse diet.

Plant use

Getting back to plant use, just recently in PNAS, an article was published about use of plants in Paleolithic times. Grindstones and pestles were used to grind starch grains, reeds, cattailes and ferns that have underground storage organs (roots). These grindstones pulverized the roots and perhaps made flour out of them. So, this is it, the diversity of diet that spread from Africa about 50 kya, and support for the hypothesis that humans replaced Neandertals because of flexibility of diet. Is this what allowed humans to be more successful?

Intensification of resource extraction, including agriculture

Bringing us into more recent time period to complete the story, 50kya humans colonized Europe and Asia and Australia. At around 15kya, they colonized the new world. So, by 10kya we have humans everywheere by 10kya other than Pacific islands and Antarctica. Diet tends to evolve and change. Humans don't stay focused on large game, and birds and fish. They intensify. What we see with intensification in the Holocene is the use of technology to extract nutrients from resources.

Steele shows pictures of mussel shells having accumulated over a short period of time. There was a heavier investment in technology. This creates a stable food supply that allows populations to grow. "We can see this in our local California native indians," she said. Just to highlight investment in technology, she shows slides on the natives' use of technology. "These are all the steps to take acorns and make it into something consumable. They're toxic, so you have to dry them, pulverize and leach them. It requires very heavy technological input."

The intensification brings with it the origins of agriculture at 10 kya. At 10kya we see changes in environment tha promote plant resources, a shift in global climate where there's more CO2, a more wet and stable environment, more admittable to plant production. People are becoming more dependent on smaller resources from agriculture. The fish, they help populations to grow and hunter-gatherer populations are more stable. It's clear from her slide that because of agriculture, there's an uptick in human population growth. Then, when industrialized agriculture arrives, there's an inflection point when we see a high rate of population growth. That's where we are today in the evolution of human diets. That's 4 million years (in 40 minutes).

Question 1: Why did humans replaced Neandertals?

The first question posed to Steele after her talk was about her thoughts were about why humans replaced Neandertals. She answered, "Yes, I think ultimately it's due to dietary differences." There's not much differences in species hunted, not so different butchery, but you do see a difference in stone artifacts and projectile points. The modern human tools were more reliable and accurate. They would've been able to obtain a larger number of reindeer, and been more consistent in hunting, along with having a more diverse diet.

The more ultimate explanation, however, was if it was cultural. Did modern humans have a more complex language? Could symbolism have allowed us to communicate in a more effective way, made our hunting more effective, that's where we're going now with the research. Language is fundamental, so if we can track where language evolved, then we'll find more answers?

Question 2: What conclusive evidence is there of cut marks?

The question asked to Steele reverted back 3.2 mya to how solid the evidence was of Australopithecus afarensis making cut marks. Steele answers that the cut marks are just as conclusive as later time periods. "If we are going to accept the later cut marks, then we have to accept the earlier," she said. "For me they're fine in terms of more recent assemblages. The challenge is to find more cut marks to see if it was widespread or a one-time thing. Who made them? Where are the stone tools?" That's the next project.

Question 3: What ratio of fatty acids in diet correspond to brain size?

Lastly, an audience member asked if recent work on long-chain omega-3s on mood disorders supports the theory that omega-3s from aquatic resources fueled brain growth. The quiestoner also mentions work by others on omega-3 to omega-6 ratios, which has changed since huntergatherer times (from 1:1-3 to 1:10 to 1:20). Could this be the reason that brain sizes are getting smaller?

Steele answers that, in general, there's body size reduction and brain size reduction. Hunter-gatherers of the anthropological record were quite robust. Now we see decrease in stature, brain size reducing, body size reducing. The change in body shape may be due to changes in diet. Whether it's omega-3/omega-6? Steele says she couldn't say for sure if that's the case.

(Note: Hat tip to @KeithNorris and @evolvify (see blog post here) for first alerting me to this new video via their tweets).