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(Image source: Wikimedia Commons)
BY JONAS BRUUN
For centuries, scientists have chased the truth about how animal ancestors swapped their
fins for limbs and crawled out of the sea. Now, researchers believe they’ve come closer
than ever to reconstruct the pivotal step in our evolution. The big breakthrough? DNA
from a fish believed to have fallen extinct 70 million years ago.
In the new study presented Wednesday in online journal Nature, scientists identified the
African coelacanth to have genes offering clues to how land animals’ hands, feet,
immune systems and other body features may have evolved.
The coelacanth — popularly called a “living fossil” for its close resemblance to ancient
predecessors — was first discovered alive in 1938. Six years ago, researchers started
decoding the coelacanth genome as its fleshy, lobed fins look somewhat like limbs. (Video
source: YouTube/NatGeoWild)
And according to the scientists, it was worth the wait as the research revealed one gene
relating directly to the coelacanth’s cousin species — the ancestor to the first tetrapod,
who invaded dry land 400 million years ago.
The International Business Times quotes one of the study’s co-authors, saying of the
research: “This is just the beginning of many analyses on what the coelacanth can teach
us about the emergence of land vertebrates, including humans, and [it] can lend insights
into the mechanisms that have contributed to major evolutionary innovations.”
So how did the researchers test whether the coelacanth DNA can make limbs? They simply
put a coelacanth gene enhancer into mice. And it proved to be powerful.
As the LiveScience puts it, “some of the fish DNA caused mice to sprout limbs”.
But the study showed the endangered fish is unlikely to be directly descended from the
first fish to walk on land. Instead, scientists now believe a more likely candidate is the
closely related lungfish. (Via The Independent)
But as a writer from The New York Times points out, the coelacanth may still have the last
laugh as the lungfish genome cannot be cracked with present methods.
“The coelacanth genome is therefore more likely to shed light on what genetic alterations
were needed to change a lobe-finned fish into the first land-dwelling tetrapod.”
The recently discovered coelacanth is one of few species to have hardly changed in tens
of millions of years. Their population numbers are not well known, but studies suggest only
a few thousand remain.