Evolution: chance, contingent or convergent (Evolution)

by David Turell @, Friday, October 27, 2017, 01:28 (25 days ago) @ David Turell

A new book presents it own argument:


"IT’S one of the biggest questions in biology: is the outcome of evolution deterministic and predictable? In particular, was the evolution of human beings, or something similar, inevitable?

"Jonathan Losos, an evolutionary biologist at Harvard University, approaches this through the contrasting views of the late Stephen Jay Gould and University of Cambridge palaeontologist Simon Conway Morris.

"Gould famously argued that if we “replayed the tape of life” we would get very different outcomes, because the pattern of evolution is unpredictable. In contrast, Conway Morris claims that convergent evolution – the idea that similar conditions produce similar adaptations – is “completely ubiquitous”.


"Losos does not explain the reasons behind Gould’s and Conway Morris’s ideas. Nor does he fully explore how their contrasting world views (Conway Morris is a devout Christian; Gould was a Marxist) influence their thinking.


"Losos’s conclusion is that neither Gould nor Conway Morris is right. Faced with similar selection pressures, similar populations will indeed often produce convergent evolutionary outcomes. Even distantly related groups, such as marsupials and placental mammals, may do this – think of the marsupial and placental moles, separated by over 150 million years.

"But the process isn’t ubiquitous. Sometimes, stuff happens and evolution goes a little crazy. In New Zealand, there were no terrestrial mammals (bats aside) until humans arrived, but in a striking example of non-convergent evolution, the islands’ birds did not evolve forms resembling mammals elsewhere that have a similar ecological niche and environment.

"Alongside the widespread phenomenon of convergent evolution, life produces many unique forms. The human lineage is one such.

"But before the reader can conclude that our uniqueness suggests we are the whole point of evolution, Losos plays his trump card: the duck-billed platypus.

"This monotreme mammal has hair and a beak, and lays eggs. Like ours, its lineage is unique in the fossil record. Losos concludes that humans are no more the end-point of evolution than is the platypus, with its singular and slightly comical assemblage of characteristics. Not all evolution is convergent, he argues, and uniqueness does not imply destiny. That seems about right."

Comment: Not right to me. The platypus is simply a side branch in the bush of life, just as I think whales are. As the author of this review notes 'life produces many unique forms'. I'm still with Conway Morris.

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