Wednesday, September 07, 2005

First chimpanzee fossils found, etc

This is a re-post of a science news excerpts post I accidently deleted:

First chimpanzee fossils found, BBC, 31 August 2005. ... The only chimpanzee fossils known to science have been unearthed in Kenya, the journal Nature reports. The three 545,000-year-old chimp teeth were dug up in the country's Tugen Hills and probably belonged to the same individual, the US discoverers say. Plenty of fossils belonging to early human ancestors, or hominids, have been found at dig sites all over the world. But until now, scientists had not identified a single fossil belonging to humankind's closest living relative. ... The teeth were excavated from the Kapthurin Formation of the Tugen Hills late in 2004. "Once you realise what they are, they're dead ringers," Professor Sally McBrearty... [said] "The thick bases of the incisors, in particular, are very characteristic of chimpanzees and also the fact that all of the teeth have thin enamel. "The molars you might think: 'maybe this is human'; but the cusp pattern isn't really right." The chimp probably died on the shore of a lake in a wet, wooded habitat. The fossil remains of hippos, crocodiles, catfish and turtles have been found at the site. And about 1km away, human fossils probably belonging to Homo erectus have been uncovered. ... Co-author Nina Jablonski ... estimates that the chimp was seven or eight years old when it died. ... The teeth seem to share more affinities with the common chimpanzee (Pan troglodytes) than they do with its "sister" species, the bonobo (Pan paniscus). But the authors say it could equally represent a member of an extinct chimp lineage. ... Many researchers have suggested that humans and chimps have occupied quite separate ecological zones since they split away from a common ancestor between five and eight million years ago. Modern chimp populations are found in tropical west and central Africa, whereas the Rift Valley is widely regarded as the "cradle of humanity" ... The new discovery demonstrates that half a million years ago, the Rift Valley contained habitats suitable for both early humans and chimps. ... Fossils Show Chimps, Humans Co-Existed, Rossella Lorenzi, Discovery News, September 2, 2005 - American anthropologists have discovered the first chimpanzee fossils, filling one of the biggest gaps in the ancient primate record. While hominid fossils abound, no one had previously found a fossil belonging to our closest living relative ... As well as providing new insight into the evolution of chimps, the landmark discovery shatters the widespread belief that humans and chimps did not coexist since they diverged from a common ancestor five to eight million years ago. The researchers found startling evidence of the cohabitation as they unearthed fossils attributed to Homo erectus or Homo rhodesiensis in the same geologic layer less than a mile away. Since modern chimp populations are now confined to wooded west and central Africa, whereas most hominid fossils have been found in the semi-arid East African Rift Valley, it has been long speculated that ancient chimps and humans diverged from their common ancestor when hominids left the jungles and moved east to the less wooded grasslands. "People used to believe that the origin of humans had to do with their leaving the forest and beginning to walk on two legs. Our discovery shows that the forest-savanna dichotomy used to explain the split between the chimpanzee and human lines does not add up," McBrearty ... [said]. ... "It's difficult to diagnose species from teeth alone. Because we have absolutely no other fossils of chimpanzees, people have assumed that chimps did not change much over time. In fact, we don't know exactly what chimpanzee ancestors may have looked like, and if there may have been a number of different species in the past that are extinct today," McBrearty said ... According to anthropologist John Hawks ... significant developments may follow the discovery. "I think the interesting thing is the hint from genetics that East African chimpanzees diverged from central African chimpanzees only relatively recently - within the past two or three hundred thousand years. If that is accurate, then these fossils must represent some extinct form of chimpanzee that no longer exists - almost a chimpanzee version of a Neanderthal," Hawks [said] ... First-ever Chimp Fossils Found, Bjorn Carey, LiveScience, 31 August 2005. The first ever chimpanzee fossils were recently discovered in an area previously thought to be unsuitable for chimps. Fossils from human ancestor were also found nearby. Although researchers have only found a few chimp teeth, the discovery could cause a shake-up in the theories of human evolution. ... It had previously been thought that chimps never lived in the arid Rift Valley-they prefer more lush environments like the Congo and jungles of western Africa. For years scientists believed that early human ancestors left the jungles and moved east to the less wooded grasslands and that this move caused the evolutionary split between the human and chimp lines. But now, with the discovery of ancient chimps and humans in the same area, evolutionists may have to rethink what caused humans to become humans. ... We need to look for another reason for the evolutionary split." ... One of the more frustrating aspects of paleontology is that full skeletons are very infrequently preserved-especially in jungle environments where soil acidity and scavengers destroy or eat bones that could otherwise become fossils. Teeth, on the other hand, more frequently survive. They’re coated with thick enamel, which protects them from chemical attacks and makes them less desirable for hungry scavengers. ... "Chimp teeth are actually very distinctive, because compared to human teeth, molars for instance, they have very, very low crowns," Jablonski said. "The incisor teeth at the front of the jaw are also very distinctive. They’re triangular and very thick - much thicker than the same tooth in a human." ... nearby Hominid fossils were also ... found in sediments of the same age as the chimp teeth-about half a million years old. Although not modern humans, these hominids were fairly advanced as evidenced by the wide variety of stone tools they used. "These represent an earlier species of human, relatives to modern humans, but not Homo sapiens," Jablonski said. "There’s some controversy over what this species is called. Most would call it an advanced form of Homo erectus. They looked like people and were a fairly sophisticated culture with various stone tools and lived in the same environment as humans." The discovery of ancient chimps and humans living in the same area opens the door to many questions. More teeth, and perhaps even bones, may lie in the Rift Valley sediments, and finding them could help answer these questions. "I’m going back to look for the rest," McBrearty said. ... [A further nail in the coffin of the Darwinian Savannah Theory of human evolution. If humans and chimps occupied the same environment, then natural selection in response to different environments cannot be the reason for their differences.]

Y Chromosome Not Going Extinct, Study Says , Malcolm Ritter, Livescience/AP, 1 September 2005. NEW YORK (AP) -- The human Y chromosome -- the DNA chunk that makes a man a man -- has lost so many genes over evolutionary time that some scientists have suspected it might disappear in 10 million years. But a new study says it'll stick around. Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself," said researcher David Page ... That agrees with prior mathematical calculations that suggested the rate of gene loss would slow as the chromosome evolved, Page and study co-authors note in ... the journal Nature. And, they say, it clashes with what Page called the "imminent demise' idea that says the Y chromosome is doomed to extinction. The Y appeared 300 million years ago and has since eroded into a dinky chromosome, because it lacks the mechanism other chromosomes have to get rid of damaged DNA. So mutations have disabled hundreds of its original genes, causing them to be shed as useless. The Y now contains only 27 genes or families of virtually identical genes. In 2003, Page reported that the modern-day Y has an unusual mechanism to fix about half of its genes and protect them from disappearing. But he said some scientists disagreed with his conclusion. The new paper focuses on a region of the Y chromosome where genes can't be fixed that way. Researchers compared the human and chimpanzee versions of this region. Humans and chimps have been evolving separately for about 6 million years, so scientists reasoned that the comparisons would reveal genes that have become disabled in one species or the other during that time. They found five such genes on the chimp chromosome but none on the human chromosome, an imbalance Page called surprising. "It looks like there has been little if any gene loss in our own species lineage in the last 6 million years," Page said. That contradicts the idea that the human Y chromosome has continued to lose genes so fast it'll disappear in 10 million years, he said. "I think we can with confidence dismiss .... the 'imminent demise' theory," Page said. Jennifer A. Marshall Graves ... who argues for eventual extinction of the Y chromosome, called Page's work "beautiful" but said it didn't shake her conviction that the Y is doomed. The only real question is when, not if, the Y chromosome disappears, she said. "It could be a lot shorter than 10 million years, but it could be a lot longer," she said. The Y chromosome has already disappeared in some other animals and "there's no reason to expect it can't happen to humans," she said. If it happened in people, some other chromosome would probably take over the sex-determining role of the Y, she said. ...[See also, Study: 'Male' chromosome to stick around, CNN, August 31, 2005 & Male chromosome may have a future after all, MSNBC, August 31, 2005. Prof. Grave's "It could be a lot shorter than 10 million years, but it could be a lot longer" is a good(?) example of an untestable theory. Apart from the unlikelihood of anyone remembering her prediction in "10 million years" time, I am sure that if the human race still existed in "10 million years", it would have long since have developed the technology to prevent any loss of essential Y-chromosome genes if it wanted too. I came across this "imminent demise" argument of Prof. Graves while doing my biology degree (she is a leading Australian geneticist) and it seemed an unwarranted extrapolation (to put it mildly). The Y-chromosome's primary (only?) function is determing the sex of males. Therefore, that the Y-chromosome it can lose other genes that have no essential function does not mean it can lose its primary function maleness-determining SRY gene(s). If that happened, then (absent any genetic engineering solution or Prof. Graves' vague `hand-waving' "some other chromosome would probably take over the sex-determining role of the Y") only females would be born, leading to extinction of the species when the last male died. Here "the Y chromosome has already disappeared in some other animals" is misleading. According to Wikipedia, "only two species of `mole voles', Ellobius tancrei and E. lutescens, have lost the Y chromosome entirely. In one species, both sexes have unpaired X chromosomes; in the other, both females and males have XX." It seems they have the original generalised XX chromosomes one or both with maleness determining SRY gene(s) that never became specialised into an X and a Y chromosome as in humans? But having long since specialised its male sex determination in the Y-chromosome, that does not mean it could re-develop it again. So if any genes are going to be preserved by natural selection it would be the Y-chromosome's maleness genes!]

Deceit of the Raven, DAVID BERREBY, The New York Times, September 4, 2005 It began with apes. In the 1960's and 70's, scientists taught captive chimps to use words and documented wild ones using tools and planning hunting expeditions. Then other smart mammals -- monkeys, elephants and porpoises among them -- also proved to have surprisingly "human" mental powers. And in the last few years, the circle has expanded to still other mammals and beyond. Last year, in the journal Animal Cognition, the behavioral biologist Thomas Bugnyar described a twist in an experiment he was conducting with laboratory ravens. The birds' job was to find bits of cheese hidden in film canisters, then pry open the lids to get the food out. One raven, Hugin, was best at this, but a dominant bird, Munin, would rush over and steal his reward. So Hugin changed his strategy: when the other bird came over, he went to empty canisters, pried them open and pretended to eat. While the dominant bird poked around in the wrong place, Hugin zipped back to where the food really was. He was deceiving Munin. To do that, Hugin had to grasp that "what I know" and "what he knows" are different. He had to understand, on some level, that other ravens have their own individual perceptions, feelings and plans, just as he does. It was big news when scientists found evidence that apes could grasp this. That some birds can as well is even more remarkable. Bugnyar and his colleague Bernd Heinrich have uncovered still more evidence for avian "mind reading." In another experiment, described in The Proceedings of the Royal Society, they had ravens watch as a scientist gazed fixedly at a spot on the other side of a barrier. All the birds, apparently understanding that the big featherless biped knew something they did not, hopped off their perches to get a look. Ravens aren't the only animals getting an upgrade. Earlier this year, Brian Hare ..., Michael Tomasello ... and their colleagues showed that ordinary domestic dogs understand what is meant when a human being points at something (as in "the food's under this one!"). Even apes don't understand pointing, which suggests that selective breeding has left dogs especially attuned to reading human minds. People, of course, are expert at that -- knowing that another person's winks, nods, sighs and shrugs are not just random twitches but the signs of a mind inside that other person's body. We have an apparently effortless understanding that the person across from us has her own thoughts and feelings. That sense comes to toddlers, the theory goes, much as language does: because the capacity to learn it is "built in" to normal brains. .... The significance of research like Hare's and Bugnyar's is that it adds mind reading to the long list of skills we can't claim for our own kind only. When it comes to mental abilities, animals aren't on the other side of a chasm: birds and dogs, as well as apes and sheep, stand with us on a continuum. And even as biology establishes that animals aren't automatons, another challenge to our sense of uniqueness arises in the field of artificial intelligence. Even automatons aren't acting like automatons anymore. They're increasingly apt and lively -- less like machines and more like living minds. ... What happens, as these trends continue, to the familiar guideposts for deciding what is human? How will people decide, without a checklist of yes-no criteria for human standing, who, or what, is entitled to privileges and rights? The history of human groupishness -- our tendency to divide ourselves up by color, language, religion, sex, ideology and many other criteria -- hints at a possible answer. For millennia, humans have been capable of sending help to total strangers because they're perceived to be like us ... In 1995, Mary Tyler Moore wrote an appeal for lobsters, saying they're "fascinating beings with complex social interactions, long childhoods and awkward adolescences. Like humans, they flirt with one another and have even been seen walking 'claw in claw'! And like humans, lobsters feel pain." In other words, even as the clear list of differences between human and nonhuman gets shorter, the ancient rhetoric of Us and Them remains. People will never have any trouble dividing the human from the nonhuman. We've been doing it to one another for thousands of years. ... [This "birds and dogs, as well as apes and sheep, stand with us on a continuum," (apart from being false-that we share a common ancestor with "birds and dogs, as well as apes and sheep" does not mean we are on a "continuum" with them) is what Bertrand Russell called the "votes for oysters" fallacy:

"There is a further consequence of the theory of evolution, which is independent of the particular mechanism suggested by Darwin. If men and animals have a common ancestry, and if men developed by such slow stages that there were creatures which we should not know whether to classify as human or not, the question arises: at what stage in evolution did men, or their semi-human ancestors begin to be all equal? Would Pithecanthropus erectus, if he had been properly educated, have done work as good as Newton's? Would the Piltdown Man have written Shakespeare's poetry if there had been anybody to convict him of poaching? A resolute egalitarian who answers these questions in the affirmative will find himself forced to regard apes as the equals of human beings. And why stop with apes? I do not see how he is to resist an argument in favour of Votes for Oysters. An adherent of evolution should maintain that not only the doctrine of the equality of all men, but also that of the rights of man, must be condemned as unbiological since it makes too emphatic a distinction between men and other animals." (Russell B., "History of Western Philosophy," George Allen & Unwin: London, 1961, pp.697-698).
Indeed, if one is going to use the "stand with us on a continuum" argument, then why stop there? If all life shares a common ancestry (which I accept), then if one argues on the basis of that common ancestry that we should not "divid[e] the human from the nonhuman", then one should be arguing for equal rights for bacteria! Since the writer includes "artificial intelligence ... machines" in this "human ... nonhuman" continuum, maybe he agrees with that?! But as Antony Flew pointed out that this sort of thinking was a version of the Genetic Fallacy (see tagline quote) .]

Stephen E. Jones, BSc (Biol)
Problems of Evolution"

"The Genetic Fallacy really is a fallacy, and it consists in arguing that the antecedents of something must be the same as their fulfilment. ... Consider a recent best-seller, hailed by its delighted publishers as `a wildly successful book'. My copy of The Naked Ape reports that the reviewer for The Times Educational Supplement described it as `brilliantly effective, cogently argued, very readable'. Marshall McLuhan agreed: `As with the title, the entire book is full of fresh perception.`Explaining that wildly successful title the author says: 'There are one hundred and ninety three living species of monkeys and apes. One hundred and ninety two of them are covered with hair. The exception is a naked ape, self-named homo sapiens' [Morris D., "The Naked Ape," Corgi: London, 1968, p.9]. ... Since McLuhan went out of his way to commend the title, it is just worth pointing out that the opposites of 'naked' and .'covered with hair' are, respectively, `clothed ' and `hairless'. So any `fresh perception' here has resulted in a misdescription. It is, however, a misdescription which suits the author's purpose. This is metaphorically to strip man and, as he was to express it in a sequel `to reveal' a human animal, a primitive tribal hunter, masquerading as a civilized, super-tribal citizen ' ... [Morris D., "The Human Zoo," Jonathan Cape: London, 1970, p.248]. Certainly it can be salutary to be reminded that, whatever else we are or may become, we remain animals: 'Even a space ape must urinate' ... [Morris, 1968, p.21]. And certainly it is useful to insist that as animals we have inescapable problems generated by our fertility. But simply to identify us with our nearest ancestors on the evolutionary family tree is an altogether different thing. It is this which, again and again, Morris does: ` Behind the facade of modern city life there is the same old naked ape. Only the names have been changed: for `hunting' read `working', for `hunting grounds' read `place of business', for `home base' read `house', for `pair bond' read `marriage', for `mate' read `wife', and so on' (Ibid. p.74.). Once more: `When you put your name on a door, or hang a painting on a wall, you are, in dog or wolf terms, for example, simply cocking your leg on them and leaving your personal mark there' (Ibid. p.161). ... The nerve of the argument, and it is an argument which comes up all over the place, is that if this evolved from that, then this must always be that; or at least, it must always be really or essentially that. Yet a moment's thought shows that this argument is absurd. For to say that this evolved from that implies that this is different from that, and not the same. It is, therefore, peculiarly preposterous to offer as the fruit of evolutionary insight a systematic development of the thesis that we are what our ancestors were. Oaks are not, though they grow from, acorns; and-for better or for worse-civilized people are not, though they evolved from, apes." (Flew A.G., "Thinking About Thinking: Or, Do I Sincerely Want to be Right?," [1975], Fontana/Collins, Revised, 1976, pp.101-102)

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