All modern mammals, from the platypus to the blue whale, descended from a common ancestor who lived around 180
The results of the study are important for understanding the evolution of mammals and for conservation efforts.
The researchers used high qualitygenome sequences of 32 living species. They represent 23 of the 26 known orders of mammals. Among them were humans and chimpanzees, wombats and rabbits, manatees, livestock, rhinos, bats and pangolins. The analysis also included chicken and Chinese alligator genomes as comparison groups. Some of them are produced by the Earth BioGenome Project and other large scale biodiversity genome sequencing projects.
The earliest mammalian ancestor is probablylooked like this fossil, Morganukodon. He lived about 200 million years ago. Credit: Wikipedia, Funkmonk, Creative Commons Attribution-Share Alike 3.0
Reconstruction showed that the ancestormammal had 19 autosomal chromosomes. They are responsible for inheriting body characteristics beyond those controlled by sex-linked chromosomes (they are paired in most cells for a total of 38), plus two sex chromosomes.
Biologists have identified 1,215 blocks of genes thatoccur sequentially on the same chromosome in the same order across all 32 genomes. These building blocks of all mammalian genomes contain genes that are critical for the development of a normal embryo, scientists say.
The researchers also found nine completechromosomes or fragments of chromosomes in a mammalian ancestor whose gene order is the same as in the chromosomes of modern birds. The study shows the evolutionary stability of the order and orientation of genes on chromosomes over a long period of evolution, which is more than 320 million years.
On the contrary, the areas between these conservativeblocks contained more repetitive sequences and were more prone to breakdowns, rearrangements, and sequence duplications. They are the main drivers of genome evolution.
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