Thursday, 10 April 2014

Discovery Shows Science Changing Its Mind

Australopithecus sediba
Human 'missing link' fossils may be jumble of species - life - 09 April 2014 - New Scientist

News this week that doubt has now been cast on what had been hailed as a new species of Australopithecus showing striking 'transitional' features between these pre-hominid apes and the hominids. A new analysis by Ella Been of Tel Aviv University, Israel suggests what were believed to be the fossils of one adult female and a juvenile male found in the same location at Malapa, South Africa, in 2008 may actually be two adults and two juveniles of different species - one each of australopithecine and hominid.

This emerging dispute interests me especially because it touches on something that many creationists and other scientifically illiterate people purport to find puzzling about science. If science is the best way to discover the truth, why is it full of disputes and disagreements, often resulting in a change of mind and even a 'rewrite of the science books'. Isn't it better to stick with dogma which hasn't been changed for a couple of millennia so you know where you are?

I'll deal with that in a moment. First, the dispute and it's background.

The exciting thing about the supposed new species, named A.sediba by its discoverer, Lee Berger of the University of Witwatersrand, South Africa, was that it appeared to have a hominid lower body, complete with feet which were close to those of Homo sapiens, and the more chimpanzee-like skull and upper body of an australopithecine. As an interesting sequel to this find, the Boston Museum of Science, MA, USA, asked visitors to walk barefoot across a mechanised carpet that analysed their footprints, and found that one in thirteen had differences in foot-bone structure similar to those of A. sediba.

This suggested that modern humans might well trace their ancestry back not to the Ethiopian Highlands as 'Lucy' (A. afarensis) suggested but to much further south. Of course, this is still consistent with the picture of H. sapiens having evolved in Africa from chimpanzee-like apes which had earlier diverged from the other three African primates; the picture merely shifted further south.

So, a few years ago we had to change our minds a little. From it being fairly safe to assume H. sapiens had evolved in Ethiopia we now needed to allow for the possibility that it might have been in South Africa instead. A little less certain and a little more uncertain and a suspension of belief pending some more evidence. Now we may have to shift it back again as the balance of evidence changes.

The doubt raised by Ella Been revolves around her analysis of vertebra and lower jawbones from the supposed two individuals. She sees close similarity between the boy's vertebrae and the vertebrae of the 1.5 million year-old 'Turkana Boy' (H. erectus) while the adult female has undoubtedly australopithecine vertebrae. This suggested two different species. Then her colleague, Yoel Rak, also of Tel Aviv University, noticed a notch on the boy's lower jawbone which looked australopithecine while a similar notch on that of the adult female looked hominid. Conclusion: there are four individuals, not two; one adult female and one juvenile male australopithecine and one adult female and one juvenile male hominid, the bones of which had become intermixed.

At this point, and admittedly not being in possession of all the facts, I think I would be tempted to ask if just one adult or one juvenile bone had been duplicated, because this would be indisputable evidence of two or more partial skeletons. I assume, since none is mentioned, that none have been found. On that basis I'm inclined not to change my mind that much, just yet.

The question remains to be resolved and one thing is sure - it will only be resolved by evidence. Until that evidence is forthcoming, it remains for science an unresolved question. The interesting this is to see how science copes with evidence which seems to refute an idea. The only honest answer to the question of where the Homo genus split off from the Australopithecus genus is one which reflects the current uncertainty and the respective strength of the evidence for and against while allowing that both could be wrong.

A central tenet of evolutionary theory is that variation within taxa becomes variation between taxa as species diverge.

Lee Berger, University of Witwatersrand, South Africa
Of course, those with an interest in one side or the other will champion their particular views. Lee Berger says that the position of the bones as found makes it likely that they were from one individual. He concedes that the juvenile vertebrae do look like H. erectus but suggests that they would lengthen as he grew to become more australopithecine. To which Been points out that other fossil Australopithecus children have long vertebrae.

Berger also argues that Been's and Rak's analysis would also make sense if A. sediba really was transitional between Australopithecus and Homo because a mixture of features is exactly what we would expect as species diverge over time.

All this is mere detail, of course. It actually matters not at all whether humans evolved in South Africa out of A. sediba or in Ethiopia out of A. afarensis, or out of an as yet undiscovered species. There is little doubt that we evolved in Africa. And even if someone were to discover that modern humans evolved in Europe or Southeast Asia after all, then that would be sensational but nothing more. We would not need to change anything other than our minds, the next editions of the textbooks and some museum displays. And our knowledge would move a little closer to the truth, which remains the truth regardless of our beliefs.

So why is this a better way to determine the truth than going with dogma, and what's the use of 'truths' that keep being disputed and changed?

Imagine you're in court, on trial for something you didn't do. One witness produces evidence which suggests you are guilty and another produces evidence which suggests you are innocent. Would you want the defence and prosecution teams to argue and debate the merits of the evidence, pointing out the flaws in it and the other possible interpretations - maybe that footprint did look like yours but thousands of people have those shoes; maybe you did once own that gun once but it had been stolen in a burglary which you had reported to the police, and the DNA at the scene was not your DNA.

Or would you want the jury to listen to someone who said it was an accepted 'fact' that people like you are criminals and there is an old book which says so, so the jury didn't need to bother with the pros and cons of the arguments over the significance of the evidence when even the experts couldn't agree. They could just go with what the old book says and save a lot of time and expense. After all, it's having an opinion that matters, not whether it's right or wrong. In any case, dogma was deemed to be right so whatever agreed with dogma would be right automatically, and the dogma said you were guilty. Why bother with a trial at all even?

Hands up those who would like to be tried by dogma and not have the jury bother with the evidence and what the experts say about it!

The point is that only by constantly reassessing and disputing the evidence can it be fully tested, assessed and appropriately weighted at the bar of informed opinion. This can only be done by people who are prepared to abandon earlier ideas and adopt new ones when the evidence changes and to whom all conclusions and 'beliefs' are conditional and transient and informed by evidence. It takes a special form of arrogance, and more than a little intellectual dishonesty, to insist that there can be knowledge without evidence. Even in the cases of a wrongful convictions, it is evidence which eventually proves the conviction to be unsafe or wrong.

Dogma is the antithesis of intellectual honesty and explains why science progresses and develops but religions remain unchanged until they cease to have any relevance and are swept aside by the tide of evidence which eventually overwhelms them or they are forced to change to avoid extinction.

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2 comments :

  1. This is something I actually read, written by an alleged human being, today, in response to a point I made:

    “Evolution???? Very questionable.... I think people need to do some research on evolution before they throw this word around... Who was Darwin??? And what were his motives??? And what does the word theory mean??? Let's do some home work please this is the man that said we came from monkeys.... For real we evolved from monkeys???? “

    “A British scientist my point exactly enough said lol let's keep European mentality where it should be .....with the Europeans thank you... And that's all I have to say about that....”

    How can one expect sense from people like this?

    ReplyDelete
    Replies
    1. Obviously not very bright. Probably a god short of the full Atheist. :-)

      Delete

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