Scientists don't know much about what the very first mammal looked like, but they do know that it lived around 180-250 million years ago and that every mammal on Earth – from blue whales to platypuses – is descended from it.
An international team of scientists has computationally pieced together a likely genome for the common ancestor of mammals by working backward from 32 genomes of living species.
Researchers concluded that the species at the very start of the mammal phylogenetic tree likely had 38 chromosomes.of the smallest chromosomes with the common ancestor of mammals, birds, and reptiles, which is a step even further back in the tree.
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