Why the evolution of humans is inevitable

16 May 2012

The 5th annual Sanger lecture was given on 3 May 2012 by Prof Simon Conway Morris, Prof of Evolutionary Palaeobiology at the University of Cambridge and a Fellow of St John's College. The Sanger lecture brings together a variety of speakers across the sciences. This year the lecture was open to members of SCI and co-organised by the Thames and Kennet group.

Prof Conway Morris is one of the leading thinkers on evolution and his thesis surrounds the idea that evolution is an inevitability. He has authored and co-authored numerous scientific papers and books on the subject.

In a lecture entitled 'Why the evolution of humans is inevitable,' Prof Conway Morris started by drawing our attention to Galileo and the beginnings of scientific enquiry. Galileo (among others) realised that theories and subsequent explanations about the world are best based on empirical observations.

Prof Conway Morris asked the audience to think about how history and therefore the present might have changed if certain key events had been different: if Hitler had won the war, if Pontius Pilate had not given Christ over to crucifixion. This naturally led to the question whether the process of evolution is based on certain inevitable milestones, or if it proceeds in a totally random fashion.

Observations from fossil records and living organisms convinced Prof Conway Morris that evolution may indeed be convergent, ie different lineages of evolution will independently develop similar traits and features. His theory has caused much controversy and challenges commonly-held views held by the biologist Stephen Jay Gould and others who think that evolution proceeds entirely randomly, and any similarities between species is coincidental.

Prof Conway Morris supports his ideas with a variety of examples where convergence of traits is evident. The 'pseudo-sabre tooth tiger' Thylacosmilus, an extinct South American marsupial was related to kangaroos and has been shown convergent on other sabre-tooth mammals, the latter being members of the felids (Carnivora). This suggests that particular dental arrangements have been found advantageous for animals and evolved independently.

Prof Conway Morris discussed the apparent convergence of eyes. It seems that eyes play a vital role for the recognition of the environment, making use of radiation in the near ultraviolet to near infra-red region of the electromagnetic spectrum. It appears that that eyes have evolved independently on several occasions and in distant organisms, in order to exploit the all-abundant radiation surrounding us. Well-known examples are our own camera eyes and the insects' compound eye.

Best known, perhaps, is the convergence between humans and cephalopods. Many cephalopods live in sunlit waters, but even in the deep sea their eyes are still employed, perhaps sensing the bioluminiscence of their prey.

Cubozoans, more commonly known as box jellyfish, are even more remarkable in that they possess eyes comprising a retina, cornea and lens very similar to our own. This enables them to see specific points of light, rather than merely light and dark. Other forms of sensoring devices, notably echolocation, have evolved independently in mammals (toothed whales/dolphins and bats) and birds (such as the oil-birds of South America).

The evidence for all these recurring features, sabre-teeth, various sensory abilities in animals and similar behaviour between distantly related species, suggests to Prof Conway Morris, that evolution is not as random as commonly thought, and nature will always converge on certain major traits, such as the eye, the ability to fly, or even intelligence.

Prof Conway Morris' excellent lecture certainly encouraged a new view on our biological history. There is evidence that suggests that, in an extreme case, the birth of another universe would always produce a very similar set of outcomes provided that the laws of physics remain the same and planets of conducive living conditions are present. If there is life beyond our own planet Earth, there is a good chance that we would recognise it as very similar to ours.

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