Photo A: Under a light microscope, the above fossil shows traces of preserved neural tissues in black. Photo B: An elemental scan of this fossil uncovered that carbon (in pink) and iron (in green) do not overlap in the preserved neural tissue. Credit: Strausfeld et al. and Current Biology.
Bones fossilize, brains do not. At least, that is what we have been taught is true. Not so, says Nicholas Strausfeld who co-authored a 2012 edition of Nature in which he reports on a fossilized brain.
“It was questioned by many paleontologists, who thought – and in fact some claimed in print – that maybe it was just an artifact or a one-off, implausible fossilization event,” said Strausfeld, a Regents’ professor in UA’s Department of Neuroscience.
His latest pater in Current Biology shows evidence that brains do in fact fossilize. Strausfeld and his collaborators look at the skeletal remains of an anthropod, which lived 520 million years ago. Nearly all of these skeletons had traces of what was undoubtedly a brain. In a different paper, Strausfeld posits that the brains were most likely able to become fossilized because of the ancient environment.
What most likely happened was that the skeleton was quickly buried so that scavengers were unable to consume the remaining brain. As long as the water has a low amount of oxygen, bacteria wouldn't be able to eat away at the brain either.
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.
“People, especially scientists, make assumptions. The fun thing about science, actually, is to demolish them,” said Strausfeld.