Hemoglobin descended from a single gene transmitted to all by their last common ancestor, said scientists from CNRS, Université de Paris and Sorbonne Université, in association with others at the University of Saint Petersburg and the University of Rio de Janeiro. The findings of the study are published in BMC Evolutionary Biology.
Having red blood is not peculiar to humans or mammals. This color comes from hemoglobin, a complex protein specialized in transporting the oxygen found in the circulatory system of vertebrates, but also in annelids (a worm family whose most famous members are earthworms), molluscs (especially pond snails) and crustaceans (such as daphnia or 'water fleas').
It was thought that for hemoglobin to have appeared in such diverse species, it must have been 'invented' several times during evolution. But recent research has shown that all of these hemoglobins born 'independently' actually derive from a single ancestral gene.
It is considered to be an animal that evolved slowly, because its genetic characteristics are close to those of the marine ancestor of most animals, Urbilateria(1). Studying these worms by comparing them with other species with red blood has helped in tracing back to the origins of hemoglobins.
This work shows that in all species with red blood, it is the same gene that makes a globin called 'cytoglobin' that independently evolved to become a hemoglobin-encoding gene. This new circulating molecule made oxygen transport more efficient in their ancestors, who became larger and more active.
Scientists now want to change scale and continue this work by studying when and how the different specialized cells of bilaterian vascular systems emerged.
(1)Urbilateria is the last common ancestor of bilaterians, i.e. animals with bilateral (left-right) symmetry and complex organs, apart from species with simpler organization such as sponges and jellyfish.