Human Evolution
emjohnson | June 28, 2009 Our newborn takes after his father.The following is something of an impromptu experiment in live birth twittering. It started out simply as a means to update friends and family, but as events transpired we received some unexpected international attention. The entire labor lasted 47 hours, involved three different locations and two surgeries. This after we had carefully planned for a natural birth with no interventions. Thank you to the hundreds of people in at least eight countries who followed our story and sent messages of support. Special thanks to Henry Gee, Senior Editor of…
razib | June 18, 200920 years ago Jeffrey Schwartz published The Red Ape, making the case that humanity's closest extant relatives within the animal kingdom were orangutans, not chimpanzees. This was contemporaneous with the media hullabaloo around African Eve, so either you could say that Schwartz's timing was perfect, or it was disastrous. Certainly he was swimming against the spirit of the age, and I recall assuming that The Red Ape was a piece of crankery when I first heard about it, its thesis was so outrageous. But historically the idea that humanity descends from Asian apes is less anomalous, and many…
razib | May 26, 2009On this week's Science Saturday John Horgan interviews Richard Wrangham. The second half of the conversation focuses on Wrangham's new book, Catching Fire: How Cooking Made Us Human. I've heard pieces of the arguments mooted in the back & forth before, but it looks like in this book they're all brought together. Humans are a large animal with a very small gut, so we need to maximize the bang-for-the buck when it comes to what we eat. Unlike gorillas and to a lesser extent chimpanzees we just aren't able to process enough low quality vegetable matter to keep ourselves going. Part of this…
razib | May 19, 2009400-500 years ago in the midst of the Great Dying somewhere the indigenous inhabitants of the New World suffered mortality rates on the order of 90-95%. This was almost certainly due to the facts of evolutionary history; the indigenous peoples had little defense against Eurasian pathogens. A result has been the reality that most of the New World is inhabited by European, African or mixed populations. But there are exceptions. In Mesoamerica there is still an indigenous dominated region from southern Mexico into the highlands of Guatemala. More substantially the highlands of the Andes, and…
razib | May 11, 2009Dienekes reports on an abstracts for paper presentations at the ESHG 2009. This was is particularly interesting:
European Lactase Persistence Allele is Associated With Increase in Body Mass Index
J. A. Kettunen et al.
The global prevalence of obesity, usually indexed by body mass index (BMI) cut-offs, has increased significantly in the recent decades, mainly due to positive energy balance. However, the impact of a selection for specific genes cannot be excluded. Here we have tested the association between BMI and one of the best known genetic variants showing strong selective pressure: the…
razib | April 30, 2009I've been fine tuning Ubuntu all day with goodies and getting drivers to work right, so I missed this paper on African genetics:
Africa is the source of all modern humans, but characterization of genetic variation and of relationships among populations across the continent has been enigmatic. We studied 121 African populations, 4 African American populations, and 60 non-African populations for patterns of variation at 1327 nuclear microsatellite and insertion/deletion markers. We identified 14 ancestral population clusters in Africa that correlate with self-described ethnicity and shared…
razib | April 29, 2009Haplotypic Background of a Private Allele at High Frequency in the Americas:
Recently, the observation of a high-frequency private allele, the 9-repeat allele at microsatellite D9S1120, in all sampled Native American and Western Beringian populations has been interpreted as evidence that all modern Native Americans descend primarily from a single founding population. However, this inference assumed that all copies of the 9-repeat allele were identical by descent and that the geographic distribution of this allele had not been influenced by natural selection. To investigate whether these…
jlynch | April 27, 2009
My colleague and friend Kaye Reed has a nice remembrance of Charlie Lockwood in the current issue of Evolutionary Anthropology. I had reason to mention Charlie during my "Last Lecture" and will admit to getting a little choked-up. The article is unfortunately behind a paywall, but any good university library should have access.
razib | April 21, 2009Neandertal birth canal shape and the evolution of human childbirth:
Childbirth is complicated in humans relative to other primates. Unlike the situation in great apes, human neonates are about the same size as the birth canal, making passage difficult. The birth mechanism (the series of rotations that the neonate must undergo to successfully negotiate its mother's birth canal) distinguishes humans not only from great apes, but also from lesser apes and monkeys. Tracing the evolution of human childbirth is difficult, because the pelvic skeleton, which forms the margins of the birth canal,…
amillikan | March 25, 2009A new paper published in Genome Research provides the most comprehensive scan to date of the genetic signatures of natural selection resulting from the last 10-40,000 years of human evolution, with some intriguing results. The results show strikingly different patterns of selection in distantly related human populations, suggesting that different human groups have adapted to their environments in different ways. Many of the regions seen to be most subject to selection contain genes of unknown function—or no genes at all—but regions linked to increased risk of type 2 diabetes showed a…
edyong | March 24, 2009Be it in sports or comedy, they say that timing is everything. In evolution, it's no different. Many of the innovations that have separated us from other apes may have arisen not through creating new genetic material, but by subtly shifting how the existing lot is used.
Take our brains, for example. In the brains of humans, chimps and many other mammals, the genes that are switched on in the brain change dramatically in the first few years of life. But Mehmet Somel from the Max Planck Institute for Evolutionary Anthropology has found that a small but select squad of genes, involved in the…
edyong | March 21, 2009
Walking on two legs, or bipedalism, immediately sets us apart form other apes. It frees our arms for using tools and weapons and is a key part of our evolutionary success. Scientists have put forward a few theories to explain how our upright gait evolved, but the 'savannah theory' is by far the most prolific.
It's nicely illustrated by this misleading image that has become a mainstay of popular culture. It suggests that our ancestors went from four legs to two via the four-legged knuckle-walking gait of gorillas and chimps. Dwindling forests eventually pushed them from knuckle-walking to a…
gregladen | March 12, 2009The following post has been slightly revised in response to commentary below and elsewhere. I thank all those who commented for the helpful critique.
The question of diversity in science, and more specifically, success for women, is often discussed in relation to bench or lab oriented fields. If you read the blogs that cover this sort of topic, they are very often written by bench scientists, for bench scientists, and about bench scientists. Which makes sense because most scientists probably are bench scientists.
But a lot of scientists are fieldworkers, and the problems, challenges and…
gregladen | February 27, 2009 This barking dog is not very smart. But it could make a good Republican. The only thing harder to understand than Michele Bachmann is the Republican Party. Bachmann is hard to understand in this way: How can a person with her mind be an elected member of congress?!?!??? The Republican party is hard to understand in this way: How can a party that is trying to become more rather than less relevant keep putting Michele Bachmann on the podium in places like the National Party Convention and, most recently, at CEPAC??!?!?!?
I can't explain any of this, but I can at least redescribe the…
gregladen | February 24, 2009Is chimpanzee food sharing an example of food for sex?
One of the most important transitions in human evolution may have been the incorporation of regular food sharing into the day to day ecology of our species or our ancestors. Although this has been recognized as potentially significant for some time, it was probably the Africanist archaeologist Glynn Isaac who impressed on the academic community the importance of the origins of food sharing as a key evolutionary moment. At that time, food sharing among apes was thought to be very rare, outside of mother-infant dyads. Further research…
gregladen | February 24, 2009Why did humans evolve hairlessness? Hair (fur) protects mammals from heat and cold, what would be the benefit from losing this asset?
I think the most commonly held theory is that fur works on quadrupeds, but once you stand upright, it is less effective, and less fur works better. For later time periods, clothing works better than fur because it is more adaptable. Consider that whatever fur-based system human ancestors had was based on needs in the tropics where it does not get that cold, so it is not hard to imagine that clothing is much more effective.
Recent studies of body parasites…
gregladen | February 24, 2009
Why did the evolution of a large brain happen only once (among mammals, and in particular, primates?)
Larger brains have evolved a number of times. It seems that there has been a trend over several tens of millions of years of evolution of larger brains in various clades, such as carnivores and primates. There is probably a kind of arms race going on among various species in which a larger brain is an asset.
However, as you imply, a really large brain (like the extraordinarily large human brain) seems to be very rare. One of the reasons for this is that there are at least two major kinds…
gregladen | February 23, 2009My student, Marta, exploded the other day.
She was sitting there in class two weeks ago and exploded. She does not know that I know this, but I noticed it happen. Since she was sitting, as usual, in the front row, and it was all in her face, the other students did not see it but I definitely did.
By "exploding" in this case I mean that her brain suddenly filled with unanswered questions, which she then started sending me in frantic emails. Many of these questions are about things we will eventually get to in class, but some are on issues that we won't touch on at all. I decided, and I…
gregladen | February 12, 2009... and made a real mess of the place when one of them spotted the jar of pickles on the counter. They fought over it until one of them had almost all the pickles and the other one had a number of bruises and a tiny fragment of one pickle that the other chimp dropped by accident.
That would be the way it would happen if two chimps walked into a bar. Or imagine two chimps, and each finds a nice juicy bit of fruit out in the forest. And instead of eating the fruit, because they are not hungry, they carry it around for a while (this would never happen, but pretend) and then accidentally run…
gregladen | February 12, 2009Or not.
Much is made of the early use of stone tools by human ancestors. Darwin saw the freeing of the hands ad co-evolving with the use of the hands to make and use tools which co-evolved with the big brain. And that would make the initial appearance of stone tools in the archaeological record a great and momentous thing. However, things did not work out that way.
It turns out that up-rightedness (bipedalism), which would free the hands, evolved in our ancestors a very long time (millions of years) prior to our first record of stone tools. The earliest upright hominids that are…