It seems that the more things change, the more a few animals stay the same.

That’s what National Geographic magazine found out when it asked Clark Honors College geologist Samantha Hopkins for help answering its Weird Animal Question of the Week: Which living mammals have stayed the same — or mostly the same — for the longest span of time. Her answer?

The platypus and the opossum. Both have been around in something like their current form for millions of years and separated from their nearest relatives tens of millions of years ago.

For the full story, see “Which Animals Have Barely Evolved?” on the National Geographic website.