Late last year, the animal evolutionary tree quaked at its root. A team led by Joseph Ryan, an evolutionary biologist who splits his time between the National Genome Research Institute in Bethesda, Md. and the Sars International Center for Marine Molecular Biology in Bergen, Norway, analyzed the genome from a comb jelly, Mnemiopsis leidyi, a complex marine predator with muscles, nerves, a rudimentary brain, and bioluminescence, and found that the animals may have originated before simple sponges, which lack all of those features.
See also: Comb jelly DNA sequence offers “unintuitive facts” about evolution…
Animal that stages light display is 600 million years old?
Sea creature, nearly 600 mya, wobbles current classifications of life
We are all denounced in the article as “temporal chauvinists” for expecting precisely what we were told in school to expect of allegedly Darwinian evolution—increasing complexity:
If comb jellies evolved before sponges, the sponges might have lost the complexity that the ancestor uniting them and comb jellies possessed. Or, that ancestor—the ancestor of all living animals—had the genes to build brains and muscles, but did not form those parts, and neither did sponges. If this is true, then comb jellies deployed the genome they inherited to build a brain, nervous system, and muscles, independent of other animals. There’s some support for this possibility: A unique set of genes seems to underlie comb jellies’ muscles.
Both hypotheses run counter to scenarios in which organisms evolve to be increasingly complex.
Casey Dunn, an evolutionary biologist at Brown University in Providence, R.I. who took part in the still-contentious comb jelly project, now doubts all notions of increasing complexity. Instead, he says the environment selects whatever form handles the challenges at hand, be it simple, complex, or plain ugly.
Gosh, he sounds a bit like that guy in a Thomas Hardy poem who lost his faith, due to reading critical works:
Since thus they hint, nor turn a hair,
All churchgoing will I forswear,
And sit on Sundays in my chair,
And read that moderate man Voltaire.
No one is allowed to ask just where the very early life forms got the complexity. It may be relevant that physicist Sean Carroll, a convert to the multiverse, is quoted on the folly of expecting the arrow to move in only one direction, so we may hear some very unusual hypotheses from such sources in the years to come.
Comb jelly lights: