AZPaul3 writes:
Will have to wait for the smart guys to chime in, of course, but right now I do not see it.
I won't claim to be a "smart guy", but I don't see it either. I just now found the article independently and was about to start a thread titled, "Dollo's Law Overturned! Scientists Baffled!" when I saw this thread.
Whatever the details of the house mite evolving gradually away from a parasitic lifestyle, it did so by way of descent with modification and natural selection. However unlikely someone wants to
post facto declare that evolutionary path, that's how it happened. It did not retrace its evolutionary history (as the article puts it but which is not exactly Dollo's Law), and it did not precisely recover a prior form, which is what Dollo's Law purports to rule out.
We usually suspect a newsperson as the source of idiocy in such cases, but after reading the article and the
Wikipedia article on Dollo's Law I'm prepared to declare that it is all three: the newsperson, the lead author, and Dollo himself.
Delila James is to be credited for doing some research and uncovering Dollo's Law, but she misapplied it to lifestyles. She apparently thought that Dollo's law prohibits a parasitic species from regaining the ability to live independently. But she wouldn't have misapplied Dollo's Law if the lead author of the paper hadn't said this:
Parasites can quickly evolve highly sophisticated mechanisms for host exploitation and can lose their ability to function away from the host body, Klimov said. They often experience degradation or loss of many genes because their functions are no longer required in a rich environment where hosts provide both living space and nutrients. Many researchers in the field perceive such specialization as evolutionary irreversible.
He meant "evolutionarily irreversible" of course, but a biologist should not state so unequivocally that an organism can't evolve back to an old lifestyle, even if the one being abandoned is parasitic. The environment will select whatever variation favors survival to reproduce without regard to lifestyle. The specific new abilities mentioned in the article, ability to digest skin and a tolerance for low humidity, do not seem particularly incredible.
What would have been amazing would be if scientists had discovered that in the process of evolving into parasites that dust mites had lost specific structures and processes, and then while evolving away from parasitism that they had regained the exact same structures and processes. They found nothing like this of course, but it is this that Dollo professes to rule out, and then Dalila James misinterpreted the head author as claiming that something like that had happened.
But lastly I blame Dollo himself for creating a flawed law. As Dawkins said in the Dollo article, it's really a statement of unlikelihood of evolutionary history precisely repeating itself. Each tiny evolutionary step is a roll of the dice, and it is self-evidently true of anything that the unlikelihood of a precise repetition increases as the number of steps increases. Because this is self-evidently true it doesn't need a "law" to say it.
But worse than that, if you consider very small evolutionary steps then Dollo's law is even self-evidently wrong because the smaller the evolutionary steps the less unlikely it is that they will be retraced. For example, life often retraces its recent evolutionary history when certain alleles in a population over time become common, then uncommon, then common again. And again and again. Like melanin in moths.
But aside from the mere statistical considerations and getting back to the dust mite, if the dust mite lost structures and biological processes necessary to an independent lifestyle earlier in its evolutionary history, then new structures and processes must have evolved, or old ones must have been turned back on, or some combination. Evolution definitely did not flow in reverse
--Percy
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