The common ancestor of all placental mammals was found "at the tip of a pen"

Apart from kangaroos and other miraculously preserved marsupials, modern mammals are placental - like the tiny furry creature scientists discovered "at the tip of a pen." It only got a chance to rise to the big stage of evolution thanks to the extinction of the dinosaurs - and today we are all its descendants.

No fossil remains of the most ancient mammals have been found, although genetic analysis shows that they could have appeared 100 million years ago, many tens of millions of years before the death of dinosaurs. All this time they led a rather miserable existence, reaching neither large size nor great variety. In fact, they only got those ecological niches that the lizards could not master.

The enormous extinction of the dinosaurs changed everything: competitors were eliminated - and our ancestors emerged from the dark holes, beginning a victorious march across the planet. Today placentals inhabit all geographic zones and number more than five thousand species, from tiny bats to multi-ton blue whales.

To understand the intricacies of their history, American paleontologists compiled a family tree, which included 86 living and extinct placentals, ordered by thousands of different characteristics. All more or less important groups of placentals, of all sizes, anatomy and lifestyles, are presented here. Where possible, comparative genetic analyzes were also carried out.

As a result, the authors showed that the last common ancestor of all placental mammals existed less than 400 thousand years after the mass extinction of the dinosaurs. The hypothetical creature was not found in the form of fossil remains and was restored only “at the tip of a pen”, based on data collected by paleontologists.

In their opinion, this ancestor was a tree-climbing, insectivorous and weighed somewhere between 6 and 245 g. It had warm fur and a long tail, and, no less important, a fairly developed brain with prominent frontal lobes and a powerful corpus callosum connecting its hemispheres .

For these animals, the disappearance of ancient lizards was the beginning of a new life and led to an explosive increase in numbers and diversity - the ancestors of key groups of modern mammals in those years appeared at intervals of no more than 200 thousand years.