Nav: Home

Eyes came before limbs in the transition to land

October 28, 2016

SALT LAKE CITY, UT (Oct. 2016) -The transition to land from our fishy ancestors is one of the most iconic, and best documented, transitions in the fossil record. We know that fleshy-limbed fish living in shallows used their limbs to move in the shallows and then up onto land, and became tetrapods (4-legged vertebrates) along the way. What has been less well-studied is the transition to vision in air that also occurred during that evolutionary event. Vision in air is different, and in some ways easier, than seeing in water. According to a new study by Malcolm MacIver of Northwestern University and Lars Schmitz of the Claremont Colleges, early tetrapod ancestors may have been seeing like land-based animals before they were moving like them.

Said Schmitz, "We were surprised to find that large eyes evolved in aquatic tetrapods, preceding the evolution of complete limbs and terrestriality." The eyes moved to the top of the head and nearly tripled in size, millions of years before the animals were fully terrestrial, and would have allowed them to hunt in a new way.

MacIver and Schmitz measured the eye sockets of over 50 fossil taxa near that transition to land as part of the study. The larger eyes at the top of the head and above the water line would have allowed for a far greater visual range, allowing them a greater diversity of behavior. Inverterbates -- insects and other arthropods -- had already moved on land, and would have been a rich source of prey. "With eyes above the water surface, fish were able to spot a cornucopia of unexploited invertebrate food on land from distances much further than aquatic prey," said MacIver.

Eyes are metabolically costly, so their increase in size must have been accompanied by a significant adaptive advantage, and this study is the first to provide a scenario for their evolution. "Animals like Tiktaalik (an early tetrapod) have their eyes on the top of their heads, suggesting that they may have hunted like modern crocodiles: swimming calmly near the surface, the head slightly raised, with eyes above the water, trying to detect prey across the water or even on land," said Schmitz.
-end-
About the Society of Vertebrate Paleontology

Founded in 1940 by thirty-four paleontologists, the Society now has more than 2,300 members representing professionals, students, artists, preparators, and others interested in VP. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.

Journal of Vertebrate Paleontology

The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.

CORRESPONDING AUTHOR CONTACT INFORMATION

Malcolm A. MacIver
Northwestern University
maciver@northwestern.edu

Lars Schmitz
Claremont McKenna, Pitzer, and Scripps Colleges
Claremont, CA
lschmitz@kecksci.claremont.edu

Society of Vertebrate Paleontology

Related Evolution Articles:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.
Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.
A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.
Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?
Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.
Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
More Evolution News and Evolution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Processing The Pandemic
Between the pandemic and America's reckoning with racism and police brutality, many of us are anxious, angry, and depressed. This hour, TED Fellow and writer Laurel Braitman helps us process it all.
Now Playing: Science for the People

#568 Poker Face Psychology
Anyone who's seen pop culture depictions of poker might think statistics and math is the only way to get ahead. But no, there's psychology too. Author Maria Konnikova took her Ph.D. in psychology to the poker table, and turned out to be good. So good, she went pro in poker, and learned all about her own biases on the way. We're talking about her new book "The Biggest Bluff: How I Learned to Pay Attention, Master Myself, and Win".
Now Playing: Radiolab

Invisible Allies
As scientists have been scrambling to find new and better ways to treat covid-19, they've come across some unexpected allies. Invisible and primordial, these protectors have been with us all along. And they just might help us to better weather this viral storm. To kick things off, we travel through time from a homeless shelter to a military hospital, pondering the pandemic-fighting power of the sun. And then, we dive deep into the periodic table to look at how a simple element might actually be a microbe's biggest foe. This episode was reported by Simon Adler and Molly Webster, and produced by Annie McEwen and Pat Walters. Support Radiolab today at Radiolab.org/donate.