This is Science Friday. I'm Ira Flato. Did you know that whales and dolphins and other cetaceans

don't make saliva? That's what I said. Well, you know, makes sense, right? If you're surrounded by

water, but they've also lost genes involved in blood clotting. Hmm. Imagine all the drastic

changes that their wolf-like land-dwelling ancestor had to go through to become the streamlined ocean animals that they are today.

A team of researchers was interested in figuring out how this evolution happened on a genetic level.

They mapped out 85 different genes that were lost in this aquatic transition, and their results

were published in the journal Science Advances.

To walk us through the genetic steps, whales, and dolphins had to go through to make it

into the water.

Meet Mark Springer.

One of the authors on that study is also a professor of biology at University of California at Riverside. Welcome to Science Friday. Thank you. It is a pleasure to be here. That's our pleasure to have you. Usually when you're studying animals from millions of years ago, you look for fossils, but in your study, you look at molecular fossils.

You know, what does that mean?

So in the genome, we have many different genes, and as you mentioned, the gene that's expressed in saliva,

it's one of the genes in cetaceans that's no longer needed. But even though a gene is no

longer needed, there are remnants of that gene that are still in the genome. It's just a dead

gene or a fossil gene, if you will. And it has mutations that have been fixed in that gene

and make it inactive. So it's a broken gene. It can't do its job.

And we were interested in looking for different genes that are broken that formerly were

functional and would have coded for different proteins. And so there are now alignments that are

available for many different mammals.

And the alignment that we worked with is an alignment of genome sequences for more than 60 different mammals,

including four different cetaceans.

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