Some have. And they are said to “turn paleontology on its head.”
F. protensa is 520 mya or so. (They had brains back then?)
Science has long dictated that brains don’t fossilize, so when Nicholas Strausfeld co-authored the first ever report of a fossilized brain in a 2012 edition of Nature, it was met with “a lot of flack.”
His latest paper in Current Biology addresses these doubts head-on, with definitive evidence that, indeed, brains do fossilize.
The only way to become fossilized is, first, to get rapidly buried. Hungry scavengers can’t eat a carcass if it’s buried, and as long as the water is anoxic enough – that is, lacking in oxygen – a buried creature’s tissues evade consumption by bacteria as well. Strausfeld and his collaborators suspect F. protensa was buried by rapid, underwater mudslides, a scenario they experimentally recreated by burying sandworms and cockroaches in mud.
This is only step one. Step two, explained Strausfeld, is where most brains would fail: Withstanding the pressure from being rapidly buried under thick, heavy mud.
To have been able to do this, the F. protensa nervous system must have been remarkably dense. In fact, tissues of nervous systems, including brains, are densest in living arthropods. As a small, tightly packed cellular network of fats and proteins, the brain and central nervous system could pass step two, just as did the sandworm and cockroach brains in Strausfeld’s lab.
What the fossil brains turn up should be interesting. Especially in view of this:
Similarly, a recently discovered 425-million-year-old crustacean showed no significant changes in internal body parts, compared to present-day specimens. One researcher called it “a demonstration of unbelievable stability.” But the stability is only unbelievable if we start with Darwin’s assumption that “natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest.” Apparently not.
We may see stranger things yet.
See also: Stasis: Life goes on but evolution does not happen
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