Human Evolution
edyong | June 14, 2008
We've all found gems hidden among junk before - the great album you own but never listened to, the book on your shelf that you never read, or the boot sale item that's worth a fortune. Geneticists are no different. Two years ago, Katherine Pollard and Sofie Salama discovered that one of the most important genes in human evolution has been lying in plain sight, hidden within a pile of genetic clutter.
Humans and our closest cousins, chimpanzees, evolved from a common ancestor, and we famously share anywhere from 96-99% of our DNA. This similarity suggests an obvious question: what are…
gregladen | April 26, 2008One of the most important evolutionary transitions in human prehistory was the rise of modern humans (Homo sapiens) from earlier hominids. A newly reported fossil from Tanzania provides an important new data point necessary to understand this transition.
Homo erectus/ergaster probably gave rise to Homo sapiens (modern humans) somewhere in Africa. It is very likely that earlier hominids (H. erectus/ergaster) and later hominids (some sort of archaic H. sapiens) co-existed, and it is also the case that during this transitional period there would be individuals with either a mixture of traits…
gregladen | April 6, 2008
Grrrrrrrrrrrrr....
Welcome to the Lucky 13th Edition of The Boneyard ... the Web Carnival about Bones and Stuff.
"The Boneyard is a blog carnival covering all things paleo, from dinosaurs to pollen to hominids and everywhere in between. It's held every two weeks (the 1st and 3rd Saturday of the month), traveling around to a different blog for each installment, connecting some of the best blogging on ancient life."
The previous edition of The Boneyard is here, at Dragon's Tales. The next edition of The Boneyard will be Here at Archaeozoology. If you would like to submit an entry to the next…
edyong | April 1, 2008You could argue that life is all about cheating death and having enough sex to pass on your genes to the next generation, as many times as possible. From this dispassionate viewpoint, human reproduction is very perplexing for our reproductive potential has an early expiry date. At an average age of 38, women start becoming rapidly less fertile only to permanently lose the ability to have children some 10 years later during menopause.
From an evolutionary point of view, this decline is bizarre. Other long-lived animals stay fertile until close to the end of their lives, with elephants…
jlynch | March 29, 2008
Seed has been running an interview with the British author Will Self whom I first encountered by reading his wonderful Great Apes, the cover of which - a mash-up of a human and ape - is above. Every time I see this picture, I can only think of one person ...
And ironically, Duane Gish says there is no evidence for human evolution.
gregladen | March 27, 2008The ape human split is a bit of a moving target. In the 1970s and early 1980s, there were geneticists who placed it at very recent (close to 4 million years ago) and palaeoanthropologists, using fossils, who placed it at much earlier. During the 1980s, the ape-human split moved back in time because of the importance of sivapithecus, then later in time when Sivapithecus slipped and fell out of the hominid/hominin (human ancestor) family tree. Meanwhile the geneticists were moving towards a more and more recent split. At one point not too long ago, all the evidence converged with the split…
gregladen | March 26, 2008I have not read the paper yet, but there is a news report out. This will be in tomorrows nature:
MADRID, Spain - A small piece of jawbone unearthed in a cave in Spain is the oldest known fossil of a human ancestor in Europe and suggests that people lived on the continent much earlier than previously believed, scientists say.
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The researchers said the fossil found last year at Atapuerca in northern Spain, along with stone tools and animal bones, is up to 1.3 million years old. That would be 500,000 years older than remains from a 1997 find that prompted the naming of a new…
gregladen | March 21, 2008... according to a new study published in the Proceedings of the National Academy of Sciences. The study compares skull measurements of Flores material with a wide range of other hominid data and concludes that Flores cannot be clustered with Homo sapiens. This is the first published study that takes into account how size affects shape. By correcting for size, this study makes, the authors claim, a more valid comparison between measurements taken on the Flores material and other comparative data.
We show that whether or not the effects of its small cranial size are accounted for, the…
gregladen | March 9, 2008It almost seems like there are two separate research project under way regarding the evolutionary history of Homo sapiens. One focuses on recent humans, tends to use DNA as a major source of information, and from this base projects back into the past. This approach tends to confirm the idea that humans share an African origin with a subsequent spread from Africa, with various degrees of complexity in that series of historical events. The other focuses on early human remains, sometimes including remains that would be placed by some in a separate species or sub species. This sort of…
gregladen | March 6, 2008There is a new paper out suggesting that the Flores hominids, known as Hobbits, were "human endemic cretins."
From the abstract of this paper:
... We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including…
gregladen | March 3, 2008A colleague and grad student of mine, Rob, just sent me the following question, slightly edited here:
A student in my intro class asked me a good question the other day to which I had no answer. When did smiling cease to be a threat gesture? I have a couple of ideas. One is that with reduced canines, smiling became a way to say "look, I have small canines, I am not a threat to you." The other is that smiling is based more on a "fear-grin" than a threat. Under this idea, smiling might have been a way of showing deference to others. If everyone shows deference, it would be egalitarian, until…
gregladen | February 26, 2008A new genetic analysis of people from around the world adds further confirmation to the African origin of humans. The study of genetic details from 938 individuals from 51 populations provides evidence of how people are related and different, researchers led by Richard M. Myers of Stanford University report in Friday's issue of the journal Science.
[Read it at the New York Times]
gregladen | February 19, 2008
Fallback foods are the foods that an organism eats when it can't find the good stuff. It has been suggested that adaptive changes in fallback food strategies can leave a more distinct mark on the morphology of an organism, including in the fossil record, than changes in preferred food strategies. This assertion is based on work done by the Grants and others with Galapagos Island finches, by Richard Wrangham and me with hominids, and by Betsy Burr and me with rodents.
The reason for this is simple. There is a rough correspondence between how much energy one can obtain from a food type and…
gregladen | February 19, 2008Comparing living chimpanzees to living humans, in reference to the species that gave rise to these two closely related species, is one way to frame questions about the evolution of each species.
Generally, it is useful to address evolutionary questions by comparing two living species with the reconstructed "last common ancestor" (LCA) of those species. All of the similarities and differences between the LCA and the living form, in each lineage, represent evolutionary "stories" (that could even be worked out as hypotheses). Similarities indicate important, long-maintained adaptations, and…
gregladen | February 15, 2008Evolution: The Mind's Big Bang
I've known Shea for years ... since before grad school. Going out drinking with this guy was a little dangerous. Almost as dangerous as going out drinking with me.
gregladen | February 12, 2008"Disease" is a big word. I'd like to address this question by focusing on the difference, or lack of difference, between a poison, a disease, and a yummy thing to eat. It turns out that they may all be the same. Yet different.
Phenylketonuria (fee-null-keet-o-noo-ria), mercifully also known as "PKU" (pee - kay - you) is a disorder in which the amino acid phenylalanine is not broken down by an enzyme (phenylalanine hydroxylase) and thus accumulates in the body as phenylpyruvic acid.
This is bad because phenylpyruvic acid interferes with normal development of neural tissues.
In western…
gregladen | February 9, 2008I've not been commenting on the comments on this post about the Myers - Rue debate, but I have been reading them with great interest. The following, while not addressing most of the comments, arises from them.
In this post, I mentioned Loyal Rue's linear hierarchy of ... I'm not sure what he called it ... let's say certainty (in science). It ran something like this:
Facts
Laws
Theory
Hypothesis
Conjecture
Speculation
Absurdity
This is not exactly what he use, but close. Perhaps conjecture and speculation were reversed... but you get the idea. You think of something that might be true (…
gregladen | February 8, 2008Last night, the Campus Atheists, Skeptics and Humanists club (C.A.S.H.) presented a debate between PZ Myers and Loyal Rue on the question: Can religion and science co-exist? I witnessed this event and would like to tell you what happened.
I want to begin with a message to PZ Myers: Thank you, PZ, for your service! There are a lot of people in the twin cities who could engage in an interesting debate on religion, atheism, evolution, creationism, etc. and do an OK job, but none others have the experience and intellectual preparation (to do an excellent job) and the draw (to guarantee lots…
gregladen | January 25, 2008
Did humans wipe out the Pleistocene megafauna? This is a question that can be asked separately for each area of the world colonized by Homo sapiens. It is also a question that engenders sometimes heated debate. A new paper coming out in the Journal of Human Evolution concludes that many Pleistocene megafauna managed to go extinct by themselves, but that humans were not entirely uninvolved.
The paper by Pushkina and Raia ("Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna") examines sources in the literature and a number of databases for Eurasian…
gregladen | January 23, 2008So far no reliable reports seem to be available of a new and potentially interesting, but not necessarily earth-shattering, find in China.
China finds 100,000-year-old human skull: report from PhysOrg.com
An almost complete human skull dating back 80,000 to 100,000 years has been unearthed in central China, state media reported Wednesday.
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