Evolution of marine mammals to water life converges in some genes

January 27, 2015 by Graciela Gutierrez, Baylor College of Medicine
Credit: Wkipedia

When marine mammals such as whales, dolphins, manatees and walruses moved from land to water, a series of physical abilities —– limbs adapted for swimming, less dense bones that make them more buoyant and a large store of oxygen relative to their body size – made it possible. Yet these animals made the transition from land to water millions of years apart.

In a report that appears online in the journal Nature Genetics, an international consortium of researchers that includes those at Baylor College of Medicine looked at the genomes of these four marine mammals and compared them to their closest land kin. The genomes of the whale and dolphin were compared to that of the cow, the walrus to the dog and the manatee to the elephant.

"The Baylor College of Medicine Human Genome Sequencing Center had already done some sequencing of the dolphin and then refined the genome sequence further," said Dr. Kim Worley, professor in the Baylor Human Genome Sequencing Center and an author of the project. The Baylor Center did the sequencing of the killer whale, dolphin and walrus and The Broad Institute of MIT and Harvard in Cambridge, Mass., sequenced the genome of the manatee. The phenomena of moving from land to water happened in the subclades (subgrouping) called Cetariodactyla (which includes whales, dolphins and cows) and Carnivora (which includes walruses and dogs) and Afrotheria (which includes manatees and elephants).

The marine mammals shared the traits needed to live in a marine environment, but they developed their traits separately – a process called convergent evolution.

"We were wondering what the genetic evidence for this was," said Worley.

In their work, they found 191 genes likely to be associated with the move from land to sea that were selected during evolution across the four species, eight of these had undergone identical changes in the different lineages. Another seven genes  had undergone identical changes but were believed to be involved in the land-sea shift in only a couple of the mammals.

The comparison of the genomes of the marine mammals has highlighted "parallel molecular changes in genes evolving under positive selections and putatively associated with independently evolved, adaptive phenotypic convergence," the authors wrote. They also found widespread molecular convergence in the land animals.

"Our data therefore indicate that, although convergent phenotypic evolution can result from conver gent molecular evolution, these cases are rare, and evolution more frequently makes use of different molecular pathways to reach the same phenotypic outcome," the authors wrote.

"We found some positively selected genes that were selected on all lineages," said Worley. "We found that there were parallel, non-synonymous changes in coding genes that occurred at the same amino acid site on more than one lineage. We also found similar history in the terrestrial animals."

Explore further: Scientists uncover genetic similarities between bats and dolphins

More information: "Convergent evolution of the genomes of marine mammals." Nature Genetics (2015) DOI: 10.1038/ng.3198

Related Stories

International team completes genome sequence of centipede

November 25, 2014

An international collaboration of scientists including Baylor College of Medicine has completed the first genome sequence of a myriapod, Strigamia maritima - a member of a group venomous centipedes that care for their eggs ...

Recommended for you

Space-inspired speed breeding for crop improvement

November 16, 2018

Technology first used by NASA to grow plants extra-terrestrially is fast tracking improvements in a range of crops. Scientists at John Innes Centre and the University of Queensland have improved the technique, known as speed ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (3) Jan 27, 2015
"When marine mammals such as whales, dolphins, manatees and walruses moved from land to water" is not quite accurate, and leaves room for those who do not understand how evolution works to inject their nonsensical objections.

It should properly state "When the ancestors of marine mammals such as whales, dolphins, manatees and walruses moved from land to water..."
5 / 5 (4) Jan 28, 2015
When marine mammals such as whales, dolphins, manatees and walruses moved from land to water....

Whatever scientist believes such nonsense is in need of much help. Evolution fanatics come up with more preposterous propositions every year. Unsubstantiated and unproven pseudo-science at best.

Yeah, because your god gave them vestigial rear legs just to test us.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.