(ORDO NEWS) — All modern mammals, from the platypus to the blue whale to humans, descended from a common ancestor who lived about 180 million years ago, during the Jurassic period.
We know little about this mysterious animal, but now scientists have been able to reconstruct its genome by computer.
Once upon a time, a tiny animal ran under the feet of dinosaurs, resembling either a mouse or a large shrew.
It rummaged through the fallen leaves in search of insects and, with the onset of morning, hid in a hole, almost without attracting anyone else’s attention.
However, this modest-looking animal was the last common ancestor of all crown mammals, that is, mammals in the strict sense of the word, without a whole list of extinct “near-mammals”, or mammaliaforms.
Unfortunately, not a single fossil has been preserved from this unique animal, and scientists can only judge what this animal looked like based on the structure of other primitive mammals. But they managed to reconstruct his genome.
To do this, the researchers collected data on the genomes of 32 modern mammalian species, representing 23 of the 26 existing orders: wombats and rhinos, chimpanzees and humans, manatees and cows, bats and rabbits.
The analysis also included data on the genomes of domestic chicken and Chinese alligator as a comparison group.
As a result, it turned out that the common ancestor of modern mammals most likely had 19 paired autosomes (chromosomes that are the same in male and female organisms) and two sex chromosomes. That is, only 40 chromosomes – the same number, for example, in a house mouse .
The scientists also identified 1215 blocks of genes that are sequentially found on the same chromosome in the same order in all 32 genomes studied. This means that with a high degree of probability they were also present in a common ancestor.
Curiously, nine complete chromosomes and their fragments matched in all studied mammals and domestic chicken. In other words, these genes have remained stable for more than 300 million years, since the separation of the evolutionary lines of birds and mammals.
Reconstruction of the ancestral genome is important not only from a general scientific point of view: by understanding how genes change in response to changing environmental conditions in different evolutionary lines of mammals, scientists will be able to evaluate the effectiveness of measures to preserve the genetic diversity of modern mammals. And this is critical for many endangered species.
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