Not So Rapid Eye Movement

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

The bizarre metamorphosis that occurs in halibut and other flatfish had even Charles Darwin floundering for an explanation. At birth, these fish have one eye on each side of the skull, but as adults, both eyes reside on the same side. Certainly, for fish that spend their lives along the sea bottom, having both eyes topside confers a survival advantage. But there seemed to be no evolutionary reason to start down the gradual path toward such lopsidedness—any intermediate steps would not seem to be especially helpful. So some biologists theorized that the fish evolved from a single, sudden mutation.

That does not seem to be the case: Matt Friedman of the Field Museum in Chicago reports finding some missing links. He investigated two roughly 50-million-year-old primitive flatfish fossils hidden in museums in Europe for more than a century. These adult specimens possessed somewhat asymmetrical skulls that nonetheless kept eyes on opposite sides of the head. Even incomplete lopsidedness may have given the carnivorous bottom dwellers a better view of the world above than no asymmetry at all, Friedman conjectures. Eye the study in the July 10 Nature.

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American