Studies have confirmed that hippos are related to whales when it comes to mammals. The first definitive whales date back to around 53 million years ago, but hippos only 16 million years. The gap between the whales’ ancestors and hippos is about 40 million years.

Australia has been home to kangaroos for about 20 million years. The first distant cousins of kangaroos lived in forests when the climate in Australia was wetter, but they went extinct 10-15 million years ago. Another interesting fact about these kangaroo ancestors is that they didn’t hop on 2 legs, but they walked on 4.

Hyenas first appeared 22 million years ago and they were very similar to today’s African civet, the earliest hyena species ever described. The ancestors had longer legs and pointed jaws.

The oldest DNA signature of the crow ancestors is 30 million years old and it was found on an island north of Australia.

For 30 million years koalas have been walking the Earth. They have been alive since Australia was already separated as a continent, which means that, most likely, koalas only lived there. During these years, it’s assumed that there have been different species of koalas.

The ancestors of ostriches come from birds today known as Palaeoits. The oldest fossils were discovered in the 1930s in central Europe, which showed they have been on Earth for about 40 million years. However, the fossil records of modern ostriches date 20 to 23 million years ago.

Due to their light bones, bat fossils are hard to locate. However, the few that have been found have given us some closure as to how long they have been on our planet. So, the earliest fossil dates back to more than 52 million years ago and it was found in Wyoming, in the United States, in 2003.

Elephants are also one of the most resilient animals. More than 300 species have been walking the Earth for 55 million years. The first known species is believed to be as big as a pig and lived in a swampy environment.

The oldest penguin fossils date back to 62 million years ago. However, the ancestors of the penguins we know today date back to tens of millions of years ago. The gap between these 2 has raised many questions, especially about what happened to the older ones.

Rats are all over the planet, especially where humans are. While there are 2,200 species in total, the most well-known are beavers, guinea pigs, squirrels, and mice. Rodent-like creatures have been on Earth for around 66 million years, which means they appeared right after the extinction of the dinosaurs.

The alligator’s ancestors evolved about 245 million years ago, however, the closest relatives to alligators, the crocodilians, appeared 80 million years ago, which are also related to crocodiles. Even though many animals went extinct in this time period, it’s still unknown why the alligators survived.

Snakes have evolved from 4-legged reptilians, probably from landbound lizards or marine reptiles that are known to have appeared on Earth 100 million years ago. Just like bats, most snakes are small and have fragile bones, which makes it difficult to find their fossils.

Even though some believe that the octopus came down from space on an icy meteor as eggs, some scientists believe that they have been on Earth for 135 million years. Octopus are closely related to squids, it’s only their nervous systems that differ.

The first ants appeared 140-168 million years ago and this means that they existed together with the dinosaurs. However, before plants there were flowers but they weren’t as widespread as they are now. Once the flowers started to blossom, the ants started to multiply even more.

Today there are still lizards that resemble the ancient reptiles that existed when the dinosaurs were still roaming the Earth. However, lizards have been on the planet for around 200 million years and today there are more than 4,675 species, including skinks, monitors, Gila monsters, geckos, chameleons, and iguanas.

Turtles have been walking the Earth for 200 to 300 million years and this makes them very ancient animals, especially when compared to humankind. The oldest fossil was found not too long ago (in China’s Guizhou province in 2007) and it was 220 million years old.

The oldest frog fossil ever found is 265 million years old and it was discovered in Madagascar. Today there are frogs all around the world, but the most concentrated area is the tropical rainforest.

Millipedes are resilient and successful creatures. They have taken care of vegetable waste for 420 million years. In fact, they were the first to move on land and some of the oldest fossils ever found. Today there are more than 13,000 millipede species on every continent except Antarctica.