A giant furry creature and a tiny mole-like animal that is only an inch long are just some of the animals, both living and extinct, featured in the new "Extreme Mammals" show.
"The exhibition explores the diversity of our closest relatives," said public program director Carol Tang.
Close, as in we all breathe air, have backbones, and nurse our young. After that, there a lot of differences, too.
"Indricotherium is the largest land mammal that ever walked the earth," explained director of communications Stephanie Stone. "It weighed up to about 20 tons, so three to four times the size of a large African elephant."
Indricotherium lived about 30 million years ago. You might have been too scared to walk up to the real thing, but visitors are allowed to touch the recreated version.
There is also the walking whale. Forty million years ago it was the link between land animals and whales.
"It walked on land, kind of wobbled around," described Tang. "But most likely it was already living in the water."
The academy has been hurrying to get the exhibit ready for the public. The show was created by the American Museum of Natural History in New York. It took 11 trucks to get it all to San Francisco.
"There are well over a hundred crates that are delivered on site and then as we unpack the crates, we put everything together," said installer Justin Steeve. "It's very much like a very big puzzle."
The exhibit also features evidence of extreme climate change. One scene shows Ellesmere Island at the far north of Canada. Now it is Arctic country, but 50 million years ago it was tropical jungle and home to a hippo-like animal. Scientists say huge temperature swings like that could happen again.
"But this time not in the space of 10,000 to 20,000 years, but in the space of 100 to 200 years," said curator Peter Roopnarine, Ph.D.
One way mammals have adapted to those changes is the evolution of our teeth.
"Teeth of very different shapes and sizes, specialized for doing different things," said Roopnarine.
You can find examples in the saber tooth tiger's giant incisors and in another creature whose teeth actually grew out its skull and through the roof of its mouth.
Ninety-nine percent of all the mammals and other species that ever lived on Earth are extinct, and we still have a lot to learn about them.
"There are some specimens in here that most scientists have never seen," said Tang.
A new discovery of a 47-million-year-old primate is one of the most complete fossils of its era ever found.
"It's important to find all the pieces of the skeleton because then you can really see even the tiniest details and really put together what it ate, how it lived," said Tang.
You can see the extreme mammals for yourself at the Academy of Sciences in Golden Gate Park. The exhibition runs through Sep. 12.
Watch this report tonight on ABC7 News at 6
Written and produced by Jennifer Olney.