Please Stand By . . .

We are experiencing temporal difficulties.

Image: Tammey Stubbs
Actually I'm just extremely busy right now with this pesky grad school business. But don't worry, The Primate Diaries will be back to its regularly scheduled programming shortly.

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Situational Science Man

Your Sunday Skepticomic from Doonesbury.

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To view last Sunday's comic click here.

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The Problem with Atheism

Sam Harris at the Atheist Alliance International Convention

In my view Sam Harris had some of the most astute comments at this year's AAI convention. The text of his speech was earlier posted at RichardDawkins.net but is now available through YouTube.

Part 1



Part 2



To view Richard Dawkins' address at the 2007 AAI Convention click here.

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Controversial and Sad

James Watson retires after promoting racist science

James Watson and Francis Crick after their discovery of DNA in 1953.

Image: A. Barrington Brown/Photo Researchers Inc.

The final chapter (one hopes) in a shameful history of scientific racism has just departed in a cloud of embarrassment. As I detailed earlier, DNA co-discoverer James Watson made the unambiguous statement that he thought Africans were less intelligent than other people, a claim he has just as unambiguously rejected.

"To all those who have drawn the inference from my words that Africa, as a continent, is somehow genetically inferior, I can only apologize unreservedly. That is not what I meant. More importantly from my point of view, there is no scientific basis for such a belief."

Watson has now announced his retirement as chancellor of Cold Spring Harbor Laboratory, where he was director from 1968 - 2003.

As New Scientist reports:

Eduardo Mestre, chairman of the board of CSHL, says Watson's contribution to the understanding of DNA "will continue to influence biomedical research for decades to come", and added that, the board "respects his decision to retire at this point in his career".

There is no doubt that Watson's past scientific work has been exemplary, however his numerous public statements have revealed him to be not only racist but also sexist and homophobic. While Watson is welcome to hold whatever opinions he likes, he does a great disservice to the public trust by representing the scientific viewpoint in such a shameless manner. I wish him well, but am glad not to have him on the public stage any longer.

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Four Stone Hearth #26

Net's best anthropology blog carnival begins its second year.

Welcome to the newest installment of the four field anthropology blog carnival Four Stone Hearth. As the carnival enters into its terrible twos there were many wonderful voices clamoring for attention. I've done my best to select only the choicest beans to make this blend a sensation you won't soon forget.

Cultural

Mango Girl at Kafr Al-Hanadwa discusses how fasting in Hinduism is perceived to have spiritual benefits, but only for women. Such is the romance of the self-denying woman.

Meanwhile, anthropologists working with the military are still raising controversy. Oh No a WoC PhD has her say about Anthro and the State while The Interrogation Diaries makes a few points about the little rituals of dehumanization. Marcus, From an Anthropological Perspective, puts it all into context by exploring the way politics affects how academics make a living (in a post which I’m not sure is a justification or an excuse).

Anthropologi reviews recent research showing that Islam and a secular society are not incompatible.

Tyson Yunkaporta at Aboriginal Rights brings our attention to the European indigenous Sami who are struggling for survival in their native land.

Peter at Indigenous Issues Today shows how indigenous people and aid organizations can work together to preserve the environment in Oaxaca, Mexico.

Linguistic

Speaking lucidly at Savage Minds, Kerim highlights a recent book that (surprise) finds the differences between how men and women communicate have been overblown.

Simon at Henry.simon.net.nz reviews the recent Nature article that shows how the less a word is used the faster it evolves.

Ed Yong at Not Exactly Rocket Science mines the classic texts to review new models for showing how verbs change over time.

Having the last word, Victor at Music 000001, explores the evolution of music and how primate vocalizations could be connected to the origins of melody.

Archaeology

Martin at Aardvarchaeology has turned up a new picture stone, with pictures no less.

Greg Laden at Evolution: Not Just a Theory Anymore, explores an 11,000-year-old wall painting from Syria.

Christopher at Northstate Science shows how Intelligent Design advocates don’t merely confine their bad analogies to evolution.

Tim at Remote Central critiques the recent Nature article that describes fishing populations showing “symbolic behavior” (they painted stuff red) in South Africa 164,000 years ago.

Leaving no stone unturned, Julien at A Very Remote Period Indeed reports Newsflash: Neanderthals could build stuff.

Biological/Evolutionary

In perhaps the most exciting thing to come out of neandertal DNA since we even had the stuff, John Hawks’ Weblog explores what the FOXP2 gene reveals about the evolution of language. Anthropology.net gives additional insight on the neandertal "language gene".

Following hard on the alleles of neandertal genetics, Anthropology.net offers their take on three recent papers exploring the diversity and structure of the human genome.

Just in case you didn’t have enough to worry about, Archaeozoo offers us something that's sure to be a big pain in the neck with the first in her new series Know Your Pathology: Osteoarthritis.

Rounding out the tour of hominin evolution, Scott at Dammit Jim! takes us home to the location of Peking Man during his recent visit to China.

Finally, to leave you all with a few warm fuzzies to carry you happily through your day, I offer these new findings of Adoption in Non-Human Primates and The Biology of a Mother’s Love.

That does it for this installment of Four Stone Hearth. The next edition will be November 7 at Sorting Out Science. Until then, keep evolving.

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Wedging Religion into Science (Again)

Answers in Genesis promotes miseducation in America

Image: Tom Toles/Washington Post
As AiG is currently attacking public science education (and, surprise, not because our science standards are ill preparing our students) I thought it would be appropriate to repost this article from the last time they tried to pull this nonsense. It's organizations like this that continue to ensure that our nation's understanding of evolution reaches a whopping 33rd out of 34 countries (just ahead of Turkey).

--

Ken Ham, founder of Answers in Genesis and creator of the Creation Museum, is currently promoting his new book by submitting sample chapters on his group's website. Entitled War of the Worldviews the book teaches Young-Earth biblical literalists strategies on how to argue against the evidence for evolution.

At the beginning of the chapter he chastises Christians for adopting “flaky evidence” to support their views.

Over the past several years, some so-called “evidence” for creation has been shown not to be reliable. Some of these are

* supposed human and dinosaur footprints found together at the Paluxy River in Texas.
* the small accumulation of moon dust found by the Apollo astronauts.
* a boat-like structure in the Ararat region as evidence of Noah’s Ark.
* a supposed human handprint found in “dinosaur- age rock.”
* a dead “plesiosaur” caught near New Zealand.

Most well-meaning, informed creationists would agree in principle that things which are not carefully documented and researched should not be used. But in practice, many of them are very quick to accept the sorts of evidences mentioned here, without asking too many questions.

Initially I was impressed. Could Ham be urging his readers to seriously engage the scientific evidence in an effort to make reasoned arguments? Alas, this was not the case. His answer to the flaky evidence that creationists have long used is, rather, don’t use any evidence at all!

When someone says they want “proof” or “evidence,” not the Bible, one might respond as follows: “You might not believe the Bible, but I do. And I believe it gives me the right basis to understand this universe and correctly interpret the facts around me.”

Let’s just apply that logic in another way, shall we? There are few scientists today who would argue that bats are actually birds rather than mammals. Pesky issues regarding bone structure and their nursing of infants make this a difficult theory to gain support for. But suppose all of the science isn’t in, the same way that all of the science isn’t in about continental drift (has anyone actually watched continents move?). Isn't there room for an alternative theory?

The Bible clearly states (Deuteronomy 14:11 & 14:18) that bats truly are birds, and they’re unclean birds at that. So by Ham's logic, this evidence deserves equal weight to that of the so-called experts. But as you’re answering a question on your zoology midterm that asks “Are bats birds?” (this is a very introductory level class) and you answer “Yes” I would encourage you NOT to attempt Ham’s suggested response to your science teacher after it's been marked wrong.

Likewise, a solid majority of astronomers (perhaps a little more) accept the evidence that the Earth spins on its axis daily and orbits around the sun. However, the Bible does clearly state that “all the earth: the world also shall be stable, that it be not moved.” (1 Chronicles 16:30). In fact, there are several passages that lend credence to the potentially lucrative field of Christian Geocentric Science (see Job 9:6-7; Job 37:18; Psalm 19:4-6; Psalm 93:1; Ecclesiastes 1:5; you get the picture).

So when someone claims there is evidence for this so-called Heliocentric Theory (afterall, it is only a theory and it's not as though anyone can feel the Earth move) you can simply tell them,

“You might not believe the Bible, but I do. And I believe it gives me the right basis to understand this universe and correctly interpret the facts around me.”

Is it legitimate to use such a response? Should the federal government force teachers to mention this competing theory in science classes? If your answer is yes, than you’ve probably purchased Ham’s book and added to his reported $125,000 yearly salary.

In a related note, as Ham is encouraging the Young-Earthers to back away from “flaky evidence” he might want to take his own advice. During a lecture criticizing the evidence for evolution last year Ham laid the following egg:

He pointed out cave drawings of a creature resembling a brachiosaur to make the case that man lived alongside dinosaurs after God created all the land animals on Day 6.

Cave drawings are evidence? That's what that crank von Däniken tried to pull. This would simply be comic, except for one thing. They're not in on the joke and are teaching hundreds of thousands of children at home schools across the country this very rubbish. They're forming think-tanks, founding law schools and funding politicians and they will not listen to reason. They're being taught not to.

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The Biology of a Mother’s Love

Mother-infant bonds predicted by hormone levels in humans and other mammals

Image: "Mother's Love" by Kolongi Brathwaite
A common tactic by evolution deniers is to claim that if a complex behavior can’t be measured than the scientific method must be a flawed approach towards understanding the world. Nevermind that no one challenges the science of physics just because we can’t predict the complex motions of a leaf in a windstorm. But when it comes to matters of emotion somehow natural explanations are off limits. This is readily apparent in the common argument that, “if you think biology is such a good explanation of behavior, then prove that your mother loves you.” However, as it turns out, we can address this challenge of motherly love and demonstrate a plausible scientific explanation by measuring the levels of the important hormones involved.

Writing in the current issue of Psychological Science (subscription required), Ruth Feldman and colleagues at the Gonda Brain Research Center at Bar-Ilan University in Israel have found evidence that neuroendocrine levels of the hormone oxytocin is a strong predictor of a mother’s bond with her infant. By sampling the blood oxytocin levels of 62 pregnant women (of all educational and employment backgrounds) the researchers found that oxytocin levels remained consistent throughout their pregnancy but differed substantially between the women. By then analyzing video footage of the mothers’ interactions with their infants (which included analysis of how often they gazed at the infant’s face, their amount of affectionate touching, rocking, and how often they spoke in motherese to their child) the researchers found that levels of oxytocin was the major factor in predicting the levels of maternal bonding.

As the authors reported in their study:

The results suggest that the neuroendocrine system associated with bond formation in mammals may play a similar role in humans. OT [oxytocin] was found to be related to a well-defined cluster of maternal behaviors, attachment representations, and a specific maternal behavior that appears across mammalian species . . . These findings lend support to ethological and evolutionary perspectives on human bonding.

Macaque mother with nursing infant.

Image: Paula Bronstein/Getty Images
In other words, for all mammals there’s evidence that high levels of oxytocin translate into a feeling of personal attachment with their infant. Earlier studies on oxytocin have shown that the hormone is also involved in pair-bonding and cooperative behavior. For example in the closely related prairie and meadow voles, the former is a pair-bonded species that shows high levels of both maternal and paternal care while the latter are neither pair-bonded nor attentive to their offspring. Work carried out by Thomas Insel at Emory University has shown that oxytocin receptor density is the primary difference between the two species.

As to why some individual’s have high oxytocin levels and others don’t is still an open question. Research on primates and rats has shown that daughters who grew up feeling safe and secure with high levels of parental investment demonstrated the same parental behavior with their offspring. It’s likely that a safe and nurturing environment (with both economic and social support for the mother) would increase a mother’s oxytocin levels and could thereby increase the amount of maternal bonding.

However, it’s important to point out that there is not one “optimal” maternal behavior for all environments. Human mothers respond to their surroundings in the same way that other species do. Whether you’re a mouse living in desert landscape or a woman in an impoverished city center, if an environment is particularly harsh it may well be more adaptive for mothers to show less maternal bonding and thereby raise an infant who will be hardened for a difficult life. It’s also important to point out that while these results are highly significant, there is more than just chemistry that influences a mother’s love. We shouldn’t underemphasize the personal decisions or the cultural influences that a woman encounters that influence her maternal behavior. To do so would be to miss the larger picture and not show our full appreciation for the sacrifices that mothers make.

While many interactions are likely to be involved in maternal behavior (both hormonal and social), this study shows that a mother’s love can be partly quantified and predicted using the tools of the scientific method. More than a final retort to my hypothetical interrogator, what this study shows is how remarkably conservative and elegant the products of natural selection can be. To think that a single hormone is identical across mammalian species and can influence one of the most profound feelings imaginable is an awe inspiring thought. To cop a quote from Darwin himself, there truly is “grandeur in this view of life.”

Reference:

Ruth Feldman, Aron Weller, Orna Zagoory-Sharon and Ari Levine (2007). Evidence for a neuroendocrinological foundation of human affiliation: plasma oxytocin levels across pregnancy and the postpartum period predict mother-infant bonding. Psychological Science 18(11):965-970. doi:10.1111/j.1467-9280.2007.02010.x

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Richard Dawkins: Tribulation Force

Your Sunday Skepticomic from Slime Culture TV

For more of Dawkins' force for reason see this post on religious belief and evil deeds.

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To view last week's comic click here.

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Adoption in Non-Human Primates

How genes for altruism can benefit strangers as well as kin

The generosity of adoption has long been considered a unique human hallmark.

Image: Shadows of Forgotten Ancestors
For decades it was conventional dogma that humans were the only species that used tools. “Man the Toolmaker” was our celebrated designation. The hominin fossil Homo habilis (or "handy" man) was even defined within our genera primarily because the skeleton was associated with stone implements. However, when Jane Goodall discovered chimpanzees using modified sticks at Gombe to “fish” for termites, Louis Leakey famously cabled her that:

“Now we must redefine man, redefine tool – or accept chimpanzees as human.”

By now people should stop insisting on singling out specific human behaviors and declaring them to be unique in the natural world. Invariably, whatever special attributes humans possess, other primates do in some form as well. For many years it’s been argued that humans are the only primates that will adopt unrelated individuals to care for as their own. This has been conventional wisdom because it doesn’t make intuitive sense according to the rigid definition of biological fitness.

Since animals, including humans, are primarily ambulatory vehicles for their selfish genes, it would be to one's benefit to care for a niece or cousin that lost their mother but not for a stranger of which there was no genetic relation. This is because any genes that promoted such altruism towards unrelated individuals would end up losing out by using up resources that didn’t perpetuate themselves. However, these “altruistic genes” would be passed on and thrive if they were helping a kin member with similar genetic makeup. In the currency of reproductive fitness, nepotism pays.

However, in the early edition of the journal Primates (subscription required), Cristiane Cäsar and Robert John Young report on a case of adoption among a wild group of black-fronted titi monkeys (Callicebus nigrifrons) from the rainforests of Brazil.


Titi monkeys found to adopt abandoned orphans.

Image: Luiz Claudio Marigo

Since July of 2005 the team has been studying this largely unknown species, when, much to their surprise, they witnessed a new infant traveling with the group that wasn’t there previously (the authors subsequently determined that a nearby group was missing an infant). Presumably the infant got lost from its former group and ended up being saved by the latter. Even more remarkably, it was the male in the new group that provided much of the adoptive care:

“Observations of the adoptive group confirm that it was being cared for by the adult male, and initially the group’s adult female was nursing the infant alongside her biological infant. . . Thus, in the case of adoption by C. nigrifrons there is an argument to include male primates in the definition of adoption.”

This would appear to undermine the notion that only related individuals would be adopted and cared for by others. However, the authors speculate that the two groups might be distantly related, thus suggesting kin altruism as the explanation for this unique occurrence. While this could be, the coefficient of genetic relatedness would likely be much too low for such a large investment to be in the genetic interests of the adoptive parents. Furthermore, any genetic mechanism involved (let alone an epigenetic one) would be unlikely to be so precise as to differentiate a kin member from a stranger. Since any orphan they come across would have a higher chance of being from their own group (and thus closely related), a genetic “rule of thumb” would be to provide assistance to all abandoned infants so long as resources were available.

Much the same has been argued for the origin of human altruism. Since most modern hunter-gatherer populations (and presumably our hominin ancestors) live in small groups of closely related individuals, the chances of helping a kin member by behaving altruistically are very high. Our genes today are descended from such close knit communities and don’t realize that we now live in enormous populations of strangers where being generous doesn’t directly improve our reproductive fitness.

By this simple act of adopting a strange infant, these titi monkeys are teaching us an important lesson about evolutionary strategies. While the net sum of behaviors in the natural world is for the perpetuation of their genes, such mechanisms can’t always differentiate the forest for the trees. Genes that evolved for one set of environmental constraints (in this case helping the infant of a kin member) could promote behaviors for another (helping the infant of a stranger). This should give us some hope as political commentators suggest that our world is spinning out of control as the result of factionalized groups based around instincts for kin networks. If we can extend our notion of kin from our local population to the global community, then perhaps we’ll find a way to help one another. Our genes are already primed to benefit their close relations, we just need to find a way to put them to use for the benefit of the human family.

Reference:

Cristiane Cäsar and Robert John Young (2007). A case of adoption in a wild group of black-fronted titi monkeys (Callicebus nigrifrons). Primates, published online Oct. 16. doi: 10.1007/s10329-007-0066-x

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Afarensis Celebrates His Third Blogiversary

What to get an anthropologist who has everything?

Talk about offering the clothes straight from your back.

Image: Joel Bentley
Famed ScienceBlogger Afarensis celebrated his third anniversary on the blogosphere recently. The traditional gift for year three is leather, so here's a suit that should serve him well.

Remember, as Tyler Durden says:

In the world I see -- you're stalking elk through the damp canyon forests around the ruins of Rockefeller Center. You will wear leather clothes that last you the rest of your life. You will climb the wrist-think kudzu vines that wrap the Sears Tower. You will see tiny figures pounding corn and laying-strips of venison on the empty car pool lane of the ruins of a superhighway.

Here's to another three years! According to tradition, appropriate gifts then would be iron and wood, perfect for our future hunter-gathering lifestyle.

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Anthropology Blog Submissions

We're waiting . . .

Image: Unattributed

Four Stone Hearth will be held right here on Oct. 24th. Send in your anthropology related blog posts (cultural, linguistic, archaeological or biological) to primatediaries@gmail.com now.

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Intelligent Design's Selective Moral Outrage

James Watson, Ann Coulter and the tolerance of bigotry

Image: Voices for Change Committee

The nineteenth-century American author and moralist T.S. Arthur once wrote, “We are judged by the company we keep.” While we can doubt the veracity of this statement in every particular (after all, this famous advocate against the evils of alcohol was a friend of Edgar Allen Poe who probably died from drink) it’s certainly true in the case of people who condemn in others what they tolerate amongst themselves.

Denyse O’Leary, Canadian journalist and Intelligent Design creationist who writes at William Dembski’s site Uncommon Descent, has taken great umbrage with James Watson for yesterday’s racist comments, and for good reason. Just days after insulting the intelligence of Rosalind Franklin (the geneticist he refuses to credit as one of the discoverers of DNA) Watson claimed that he was “inherently gloomy about the prospect of Africa” because:

"All our social policies are based on the fact that their intelligence is the same as ours – whereas all the testing says not really . . . people who have to deal with black employees find this not true."

This is patently offensive nonsense. How such a formerly brilliant mind could believe such absolute hogwash is a depressing thought. However, it takes tremendous hypocrisy on the part of Uncommon Descent to paint these absurd remarks with a broad brush and vehemently assert that “legitimized racism is an inevitable consequence” of evolutionary theory. Considering that they have such high standards, one would naturally assume they’d call out such vile language in those they agree with as well as those they don’t.

Predictably this isn’t the case. Ann Coulter (who has said about Muslims that “We should invade their countries, kill their leaders and convert them to Christianity” - also see below) has been praised repeatedly on the same website which now claims such profound moral indignation.

William Dembski himself has stated that Coulter “will propel our issues in the public consciousness like nothing to date” and was “happy to report that I was in constant correspondence with Ann” while writing her book Godless, in which she defends the racist social science propagated in The Bell Curve.

O’Leary likewise accuses Richard Dawkins of being anti-Semitic for making passing reference to the successful “Jewish lobby” in Washington. But when Coulter announces that Jews are nothing but “imperfected Christians” and that the entire religion of Judaism should be thrown away there is strangely no mention, no moral outrage, no condemnation that “legitimized bigotry is an inevitable consequence” of conservative Christianity (which I don’t think it has to be, though believers often attempt to dissuade me of this view).

James Watson deserves the public thrashing he’s currently receiving, and I’m glad that Uncommon Descent will agree that such racist comments are despicable. However, I think this hypocrisy represents a fundamental difference between Intelligent Design advocates such as O’Leary and Dembski and those they intend to malign. Immediately after Watson’s diatribe was uttered, prominent evolutionary scientists condemned his opinions and were rightly offended by his remarks. I’m still waiting for similar actions to be taken by those pillars of tolerance over at Uncommon Descent.

UPDATE: For more on this see Mark's terrific post today at Denialism Blog.

Additional quotes by Ann Coulter:

"Jihad monkey talks tough; jihad monkey takes the consequences. Sorry, I realize that's offensive. How about 'camel jockey'?"

"I'm all for public flogging. One type of criminal that a public humiliation might work particularly well with are the juvenile delinquents, a lot of whom consider it a badge of honor to be sent to juvenile detention. And it might not be such a cool thing in the 'hood to be flogged publicly."

“Thank God the white man did win or we would not have the sort of equality and freedom, or life, that we have now.”

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Jane Goodall - A Personal Tribute

Primatologist and UN Peace Messenger at Duke University

Jane Goodall bridged the divide between two species.

Image: Hugo van Lawick
The primatologist and neuroscientist Robert Sapolsky once wrote that, when he grew up he wanted to be a mountain gorilla. Me, I wanted to be a chimpanzee. His inspiration was Diane Fossey, but I was always most interested in the work by that other cover girl of National Geographic. As I’m sure was the experience for many of us, Jane Goodall was the only scientist I had ever heard of when I was growing up (I wouldn’t discover Carl Sagan until much later). Her friendly manner and relaxed charm was a stark contrast to the cold and cerebral stereotype of Hollywood films.

So it was a great pleasure to finally hear her speak in person after a lifetime of listening to her voice from the old, tinny speakers of my family’s television. As one of the 300 speaking engagements she’ll make this year alone, Dr. Goodall addressed the Duke University campus with a message that was both a warning and an encouragement.

Covering a wide variety of topics -- from her childhood love of animals, to chimpanzee psychology, to industrial farming to global warming -- her presentation was a mixture of great challenges for this generation along with her own story of how she overcame personal adversity. However, I felt her greatest strength was in relaying the interrelated problems of globalization in such a way as to make it both accessible and revealing. She impressed upon the students and faculty in attendance that we privileged elites of the world were primarily responsible for the harmful effects imposed on the developing nations through our wasteful and insatiable consumer appetites. Since we insist on saving a dime for our coffee, another acre of rainforest is burnt in order to turn a profit. While we’ll offer billions of dollars to our allies for weapons of war, we’ll balk at microcredit programs that offer the greatest potential to raise families out of poverty.

However, she was confident that our generation would rise to the challenge. Through her Roots and Shoots program they’ve initiated a program to import shade grown coffee from the highlands of Tanzania that saves both the rainforest and offers poor farmers a living wage. Likewise, by following in the lead of the Grameen Bank (last year’s Nobel Peace Prize recipient), small loans are offering the villagers around Gombe an incentive to preserve their national heritage in a way that avoids the colonial attitude of earlier aid organizations. By explaining both the large scale problems as well as the small scale solutions, the unorganized mess of our global crisis was synthesized into a digestible whole.

It’s rare to have someone present a host of world problems that feel nearly overwhelming in their magnitude and yet to walk away feeling inspired and, dare I say it, hopeful. But such is the magic of Jane Goodall. I’ll still always remember her as she was in my youth, walking through the underbrush with her binoculars around her neck and blonde hair pulled back in a hurried bunch. The Gombe chimpanzees she introduced to the world (Flo, Fifi, Freud, Goblin, and, of course, David Greybeard) were my first introduction to a line of research that would eventually consume my thoughts. While now I want to grow up to be a bonobo, I’ll never forget the woman who first showed me how wonderful it is to be an ape.

UPDATE: Sheril at The Intersection offers her perspective on Goodall's message of hope in her latest post.

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Is Religion Poison or a Cure?

Hitchens vs. McGrath at Georgetown University



Hitchens starts after a six minute introduction. The total video is 1:40.

Linked from Google Video.

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Monkey See, Monkey Don't Remember

Neurogenesis declines in the aging primate brain

Marmoset trying to remember if this bug was tasty or not.

Image: Gerald Durell
We’ve all heard that you can’t teach an old marmoset new tricks, but researchers now understand why in a study that hopes to narrow in on the cause of neurodegenerative illness. Writing in the early edition of Proceedings of the National Academy of Sciences, Benedetta Leuner and colleagues at Princeton determined that neurogenesis, or the growth of new neurons, diminishes once these South American monkeys reach sexual maturity. This decline in neurogenesis is particularly noticeable in the hippocampus, a region of the brain central to learning and memory.

This research has been demonstrated previously in rats (I participated in some of this work as an undergraduate student) but there has always been a question as to whether or not the more complex primate brains undergo the same phenomenon:

As the authors reported:

No previous studies have investigated whether primates exhibit a similar decline in hippocampal neurogenesis with aging. . . These data demonstrate that a substantial decrease in neurogenesis occurs before the onset of old age in the adult marmoset brain, suggesting the possibility that similar alterations occur in the human brain.

This is why languages are so difficult to learn as an adult while children seem to absorb them readily. Without the growth of new neural connections in the hippocampus the accumulation of information slows dramatically.


Imo, the Japanese macaque who invented potato washing,
a trait that was easily picked up by the young but not older individuals.

Image: Franz de Waal
These results have also been shown in the adoption of new cultural traditions in apes and monkeys. In the famous “potato washing” findings in Japanese macaques, it was younger females who were quickest to learn the new technique while the older males sat around on the periphery wondering what was wrong with the kids these days.

However, the authors point out the situation isn't a hopeless descent from vigorous mental youth to gum-smacking confusion in old age (although Noam Chomsky should be evidence enough of that). As author Elizabeth Gould explains to Science Daily:

"This news isn't entirely negative, though it seems to be at first glance," Gould said. "The silver lining here is that neurogenesis continues long past puberty and does not stop entirely, even in older primates. What's more, it can be stimulated with experience."

So keep keep struggling through Dostoevsky and Foucault. The mental effort will pay off in the long run.

Reference:

Benedetta Leuner, Yevgenia Kozorovitskiy, Charles G. Gross and Elizabeth Gould (2007). Diminished adult neurogenesis in the marmoset brain precedes old age. Proceedings of the National Academy of Sciences, early online edition Oct. 15.

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