The Ringtail "Cat".
A great website is at:
https://www.onezoom.orgThere one can learn that the Ringtail is part of a group of animals, 8 species altogether, of Ringtail, Coati and Raccoon. They all share a common ancestor of (roughly) 14 million years ago.
If ever you are kidnapped by an Alien and told you will be released if you can tell how long ago did humans share a common ancestor with some random mammal, give an answer of 85 million years ago. Off course, the answer depends on which mammal you are talking about. For Primates, Rodents and Rabbits, the answer will be somewhat less. For Elephants, Kangaroos, somewhat more. But an answer of 85 million years (roughly) will give you the correct answer for Dogs, Cats, Horses, Cows, Bats, Whales, etc. and even for Deer (running or not), Raccoons and Ringtails. Just over 40 per cent of all Mammal species alive today.
Needless to say, that obscure ancestor of 85 million years ago was wildly successful, in a Darwinian sense. It is the ancestor of 4,642 species our of the 5,046 species of all mammals alive today, over 90 % of all mammals. Pretty good for a single obscure specie of small Mammal using all it's wits to avoid Dinosaurs, and larger mammals. There were, no doubt, many species of Mammals alive at that time. But only one was destined to have over 90 % of the mammals alive today descended from it.
To what can we give credit for our "half" of the Boreoeutheria, the Euarchontoglires, having about 60 per cent of these Boreoeutheria species? To the Rodents who have 2,096 species, out of the 2,575 species of the Euarchontoglires group. Well done lads.
By the way, Mammal groups tend to be associated with some isolated continent that existed in the past. The "Boroeutheria" (Northern True Beasts) originated in the combined Europe-Asia-North America (excluding India) continent that was isolated from the other continents at the time.
The Atlantogenata (Atlantic) group of 99 species with a common ancestor of 89.1 million years ago containing Elephants and Sloths is associated with the combined South America-Africa continent.
And the Afrotheria (Africa) group of 69 species with a common ancestor of 84.2 million years ago containing Elephants and Aarkvarks is associated with Africa which became isolated from all other continents at that time.
These continental separations were not absolute. By some minor (or major) miracle, a small group of monkeys must of rafted across the young and much narrower Atlantic ocean to become the ancestors of the New World Monkeys of South and Central America. And Bats are very good at reaching continents of some distance apart. But an ocean barrier is still a pretty serious barrier. Early Primates existed in many parts of the world. They may have originated in North America. But they died out everywhere except Africa. Why? Probably because Rodents outcompeted and wiped out all Primates in the entire World, everywhere except in Africa, which (I assume) early Primates managed to reach (by a natural wooden raft?) but no Rodent managed to do so. So our existent today depended on Africa being isolated from the other continents for tens of millions of years. And a lucky Primate rafting adventure to Africa. And no Rodents making a lucky ocean crossing like the New World Monkeys did. To survive Darwinian competition for tens of millions of years, a group needs to be very good and get some luck along the way.
Note, for some who think they may detect a math error, 51 per cent of Mammals share a closer common ancestor to us than 85 million years ago. 41 per cent share a common ancestor with us of 85 million years ago. And 8 per cent share a common ancestor of more than 85 million years ago, perhaps as far back as 180 million years ago. Hence, in answering the Aliens question, 85 million years is only going to be the correct answer in 41 per cent of the cases, not 92 per cent of the time. But this answer still give you your best chance. Good luck.
These answers are primarily based on DNA comparisons, which provides something of a clock to tell all distantly related two species are. The more different, the farther back in time the common ancestor lived. Certainly not as accurate as measuring the age of rocks through comparing radioactive isotopes but it does give a rough measure.
In any case, don't forget to check out onezoom.org and make your own discoveries.