This little beauty is an artist’s rendition of a Placoderm – an extinct fish from close to 500 million years ago which had a significant feature that has played out into the lives of all humans today. Early fishes from this geological period had jaws, and evolutionary scientists have recognized jawed vertebrate fish as the first ancestors of the adaptive immune system, one of the most complex biological systems in existence.
Living organisms share in common an innate immune system, without which viruses and bacteria would destroy a host very quickly (hours or days). But this innate system was complimented in more complex life forms 500 million years ago with the evolution of the adaptive immune system, which reponds to specific pathogens, and has its own memory. The common cold Coronavirus, for instance, or many types of influenza, are remembered and attacked by our adaptive immune systems because we have had exposure to them already. (Obviously, this explains the virulence of SARS-COV2: our adaptive immune systems have never met it.) So thanks, ugly Placoderm ancestors of ours . . . We owe our disease-combat skills to you.
Source(s): “Origin and evolution of the adaptive immune system: genetic events and selective pressures,” Martin F. Flajnik and Masanori Kasahara. _Native Reviews Genetics_, 11, 47-59 (2010). Image, placoderm Sciencesource.com Gwen Shockey unique identifier, SS2610479 .
