I think most people are aware of the fact that humans are related to other primates such as chimps, gorillas, mandrills and probably even Curious George. As a matter of fact, humans ARE primates, which means we share a common ancestor with all other primates. The order Primate includes many species other than just humans and animals that we usually call "monkeys", it also includes lemurs and some other minor families.
However, what I was curious to know was what animals are the most closely related to humans after the primates. To find out, we need to go up the ranks in our phylogenetic tree. As seen on the image on top, primates are part of the mirorder (like an order, but bigger) Primatomorpha, which includes the order Dermoptera (yes, Greek nerds, this means something along the lines of "wing skin"). The order Dermoptera consists entirely of colugos, which are also known as flying lemurs. Despite their name, they are not lemurs and despite their appearance, they are not flying squirrels. They just happen to also be equipped with a patagium (the skin membrane they use to glide) due to convergent evolution. While this is surely interesting, colugos are quite obscure animals and I was looking for a group of animals that would be more "commonly known", even if a bit less related to humans.
We can go even higher up in our phylogenetic tree and see that Primatomorpha are part of the grandorder (like a mirorder, but even bigger) Euarchonta and have a sister order, Scandentia. Animals in the order Scandentia are referred to as "tree shrews", but again, the name is misleading because while they are indeed arboreal, they are not shrews. The image above has one example of these creatures, a tupaia, and while they are cute and all, they are still not what I would call a "commonly known animal". Also, note that the position of the order Scandentia in the evolutionary tree is actually debatable as some researchers place them as a sister clade* to the Glires.
Going one more rank up in our phylogenetic tree, we see that Euarchonta are part of the superorder (like a grandorder, but bigger, you get the idea) Euarchontoglires, which includes the clade Glires. Within this clade are found the orders Lagomorpha and Rodentia, which are both comprised of very well known animals, such as rabbits and rats. I think it's pretty cool to think that those animals are quite closely related to primates, and therefore, to humans. Probably this is why they are (sadly) used for animal testing of medicine and cosmetics, although they are also probably used because of economical reasons.
* I will one day make a post about this word, it's actually pretty interesting.
