This is another of those articles I stored away intending to deal with later, but then left them to sink towards the bottom of the stack as other topics intervened. It deals with the most significant discoveries related to the evolution of modern humans in just one year - 2013. It goes without saying that a number of them involved more of those pesky 'intermediate forms' creationists are having to work so hard to ignore so they can pretend there aren't any.
The list is based on an article by Kate Wong, published in Scientific American in January 2014. The commentary is mine. Feel free to hit creationists over the head with it.
- April 2013. Sahelanthropus tchadensis. Brain Shape Confirms Controversial Fossil as Oldest Human Ancestor | Observations, Scientific American Blog Network. Thibaut Bienvenu of the Collège de France and his colleagues managed to reconstruct the endocast of the inside of the brain case of a skull discovered in 2002 in the Djurab Desert in Chad, Africa and so infer the shape of the brain which once occupied it.
This skull was known to be from a species close to the departure point between the Homo and Pan genuses 7,000,000 years ago. From the shape of the brain and the angle of the foramen magnum (the hole through which the spinal cord passes, and other clues, they showed it was from the Homo branch albeit with a chimpanzee-sized brain, and that bipedalism had started to evolve even then. If there was ever an intermediate between humans and chimpanzees, then Sahelanthropus tchadensis was it.
This suggests a possible route for the hominids from the West African forests, across the Sahel Corridor south of the Sahara to the Nile Valley, then down to the Ethiopian highlands, the East African plains and South Africa, where the Australopithecines evolved.
See also: Earliest Human Ancestor confirmed.
- December 2013. Orrorin tugenensis. The femur of Orrorin tugenensis exhibits morphometric affinities with both Miocene apes and later hominins. The femur of this putative human ancestor from 6,000,000 years ago from Kenya, shown by Sergio Almecija of the Department of Anatomical Sciences, Stony Brook University Medical Center, Stony Brook, New York, and colleagues to have intermediate characteristics between Miocene apes and hominins, specifically the austraopiths, and distinct signs of bipedalism.
Again unmistakable signs of bipedalism in this East African hominin, fitting entirely into a picture of a species having recently diverged from the proto-Pan genus and adopting bipedalism as the mode of ground locomotion on the East African plains as the stem group for the Australopiths, later for some of them to evolve a larger brain and evolve into the hominids. Dentition, skull and upper limbs show distinct chimpanzee-like features.
- May 2013. Hominin middle-ear bones or ossicles. Early hominin auditory ossicles from South Africa. Evidence that human hearing probably evolved early in our hominin ancestors when the ossicles (the small bones of the middle ear) were found to be the same in two early hominins, Paranthropus robustus and Australopithecus africanus showing that they were almost certainly present in that form in a common ancestor. Significantly, the mallleus in both was human-like while the incus and stapes were more ape-like. Even the ossicles were transitional.
How we and our ancestors heard sounds could have had a profound effect, not only on our ability to hunt and protect ourselves in the hostile East African plains but also on our ability to communicate. It's doubtful that efficient language could have evolved without the ability to discriminate between slightly different vocal intonations, for example.
- April 2013. Australopithecus sediba. Is Australopithecus sediba the Most Important Human Ancestor Discovery Ever? Maybe, maybe not. But A. sediba certainly shows a mosaic of hominid and australopith characteristics that show how skeletal changes which eventually came to be regarded as characteristically hominid may have been relatively 'easy' for evolution to produce given the right environmental selectors. For example, with an almost human pelvis and lower limb, A. sediba walked with a rolling gait and rotated the foot inwards, suggesting bipedalism may have evolved on a different trajectory in the southern group of australopiths. This may be an adequate form of ground locomotion for moving between isolated clumps of trees, but would not have been suitable for chasing down large herbivores.
Some people see A. sediba as the best candidate for the transition between the australopiths and the hominid base primarily on the sheer volume and quality of the specimens. However, though not impossible, being geographically out of place, when all the other candidates and all the definite hominids are to be found much further north, makes this an unlikely candidate in my humble and admittedly inexpert opinion. But the A. sediba find continues to reveal masses of information about hominin evolution and while they might not be our remote great grandparents we are certainly not-too-distant cousins of them.
- June 2013. Ability to throw spears. Baseball players reveal how humans evolved to throw so well. A study of American athletes showed that the skeletal changes to the shoulder joint which gives humans this ability was present in Homo erectus.
H. erectus is believed to have been the immediate ancestor of H. heidelbergensis which gave rise to H. sapiens and H. neanderthalensis and probably the still to be scientifically named Denisovans, and maybe to H. antecessor. It was also probably the first hominid to migrate out of Africa and may have been the ancestor of H. floresiensis.
This ability to throw a spear with force and accuracy would have given hunters an great advantage over large herbivores because they could kill at a distance and ambush from behind cover. They could also attack and kill other competing predators and may well have exterminated some of the large African predators and competitors.
- October 2013. The Dmanisi skull. Skull suggests three early human species were one. The remains being unearthed at Dmanisi in Georgia, south of the Caucasus Mountains are all of H. erectus from the same place and time so there is little doubt that they are all of the same species, yet the range of variation overlaps that of several African species currently assumed to be different species. If this interpretation is correct, this would simplify the human evolutionary tree considerably and even raises the possibility that H. neanderthalensis and the Denisovans could have evolved in Euro-Asia directly from H. erectus.
From a scientific point of view, this sort of information, which causes scientists to take a step back and reassess current thinking is part of the stuff of science. New information is expected to cause us to revise our opinions. Science, unlike religion, is an objective process where the truth is sacred and conclusions must be changed to get closer to it. The only opinion worthwhile holding is one supported by the best available evidence. By contrast, religion is about confirming sacred conclusions, even and often at the cost of ignoring observable evidence. The truth is assumed to be known in advance of evidence and evidence which fails to confirm it is assumed to be wrong and so can be dismissed.
- December 2013. Homo erectus hand. Human Hand Fossil Turns Back Clock 500,000 Years on Complex Tool Use. A 1.4 million year-old fossil hand bone from H. erectus suggests that they had the same dexterity and strength to manipulate and use complex tools that H. sapiens has. Previously, this was thought to be a unique characteristic of modern humans.
This fossils was from the Lake Turkana area of Kenya where the first 'Acheulean tools' were discovered. It is believed that there were also species of Australopiths co-existing in the area at this time, so the ability to make and use relatively sophisticated tools may have given our immediate ancestors the edge over these cousin species.
- December 2013. Paranthropus boisei. First Partial Skeleton of a 1.34-Million-Year-Old Paranthropus boisei from Bed II, Olduvai Gorge, Tanzania. Previously, the only remains attributed to P. boisei were cranial and dental. This find in Olduvai Gorge, Tanzania provides more information for this sister genus of Homo and suggests P. boisei was a very robust species, and probably lived on trees. Paranthropus, like Homo, are believed to have evolved from late Australopiths in the same general area of Ethiopia/East Africa, suggesting that ground-dwelling and arboreal Australopiths diverged as each became specialised in its particular environment.
- October 2013. Rising Star Cave fossils discovered. Over 1700 hominin fossils have been found in two chambers in the Rising Star cave system. Unlike the normally, and understandable secrecy which accompanies these finds, because of the security problems and the need to keep the site as undisturbed and free from contamination as possible, this site has been the subject of intense media coverage under the supervision of Witwatersrand University and National Geographic Magazine.
See also Chamber of Secrets Has Creationists in Denial Again
- December 2013. Denisovans in Spain? Earliest Human DNA Shows Unforeseen Mixing with Mystery Population. Recovery of DNA from a femur from the Sima de los Huesos (‘pit of bones’) in northern Spain, the oldest homid DNA recovered to date, show the population were probably not H. neanderthalensis or H. heidelbergensis as had been assumed, but were closer to the Denisovans, previously only know from DNA recovered from the Denisova Cave in Siberia. Denisovan DNA has also been shown to be present in several South-East Asian and Oceanian peoples suggesting that Denisovans were a predominantly South-East Asian people.
This find suggests they may once have been far more widespread - the sort of find that causes a re-think of current opinion.
- December 2013. Neanderthal DNA sequenced. The complete genome sequence of a Neanderthal from the Altai Mountains. The complete genome of a female Neanderthal from the Altai Mountains shows that this population was highly inbred with her parents being half-siblings and evidence of of incest in her immediate ancestors.
Since Neanderthals were believed to have lived in small, isolated family groups over the vast expanse of Europe and Asia where it might have been possible for one to live a normal lifespan yet never meet someone from outside his or her small clan, this is hardly surprising, but it may have made Neanderthals vulnerable to genetic defects and lacking the genetic diversity to adapt to rapid environmental changes such as would have occurred towards the end of the Ice Age.
The same study also showed that there was occasional gene-flow (interbreeding) between the Denisovans and Neanderthals, and between an unidentified hominid and Denisovans, as well as between Neanderthals and modern humans. Tantalisingly, is this unidentified hominid H. erectus? This shows that at this stage in human evolution if Euro-Asia, at least three and possibly more incompletely differentiated species acted like a ring species with H. sapiens being the sole survivor. Human evolution was in action across the hominid range, with hybridization, genetic isolation causing local extinctions and competition for resources playing a different role in different areas.
|Phote credit: John Hawks|
So the human evolutionary story continues to be unravelled with some discoveries bringing greater clarity and others raising more questions than they answer, and all the while we move closer to the truth, which only makes any sense at all as a gradual evolutionary process of diversification, selection and survival of those best fitted to produce most descendants.
And not a single discovery to support special creation or even the notion that Darwin was fundamentally wrong. No wonder creationists hate science and won't look at the evidence.
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