The genes of large white sharks oppose the scientific explanation.
An animal’s genome can be deeply revealing, but since then the researchers have begun decoding Awesome white shark (Carcharodon Carcharias)) DNA More than 20 years ago, their discoveries raised more questions than answers.
In 2024 a exploration He confirmed that, contrary to general thought, this cruel ocean predator does not belong to a single global species.
Instead, there seems to be three separate groups, all originating from a common population that lived 10,000 years ago before the last ice age reduced their number. One of the modern groups is in the North Pacific, one in the South Pacific and the Indian Ocean and one in the North Atlantic and Mediterranean.
Related: A surprising discovery reveals that there are 3 different types of great white shark
No matter how researchers try to explain these groups using evolutionary simulations, they continue to hit a dead end after a dead end.
“The honest scientific answer is that we have no idea” He says Senior author of the study Gavin Nailer, director of the Florida shark research program at the Museum of Natural History in Florida.
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While the nuclear DNA of all three shark groups is the same, their mitochondrial DNA is surprisingly different.
The nuclear DNA is packed inside the core of the cell (hence the name), but the mitochondrial DNA is packed inside the mitochondria, which extracts energy to the cell.
Unlike the nuclear DNA that is inherited by both parents, it is believed that mitochondrial DNA (MTDNA) is inherited from the mother in most Multicellular animals – Sharks includedS
Since MTDNA can trace the mother line, conservation biologists have been using it for years to identify population and migration tract limits.
However, when it comes to great white sharks, this method does not work.
Even after using one of the largest data sets for great white sharks, globally, researchers came out empty-handed.
Previously, scientists suspected that changes to MTDNA were due to female sharks who return to their hometown to reproduce – a concept known as a female philopathy.
The hypothesis is even supported by recent observation evidence which suggest That while both male and female sharks travel huge distances, women return home when it’s time to mate.
However, when Naler and his colleagues put this idea of the test, however, she failed to explain the MTDNA groups. Including the genes of 150 white sharks from around the world, Naler and his team found no evidence of female philopathy.
A small signal would be expected in nuclear DNA if women reproduce only with certain populations. “But this was not at all reflected in nuclear data” He says Nyler.
Even when the team manages an evolutionary simulation, showing how the sharks may have split into three groups after their last shared ancestor, the female hypothesis of the philopathic did not stand.
“I came up with the idea that gender ratios may be different – only a few women contribute to the one -generation population to the next,” Nayler explains.
This also failed to explain genetic differences. So they made casual genetic changes that accumulate over time, called genetic drift.
The team of scientists claims that “alternative evolutionary mechanism must necessarily work.”
But the only other known explanation offers natural selection may have refined the MTDNA of each group and that looks far away. There are only 20,000 large white sharks in the world, which is a very small population, relatively speaking. If there is anything useful in the evolution of some forms of MTDNA, then you will have to save the sharks from something “brutally deadly,” Nayler says.
He doubts this is the case. A piece of puzzle is obviously missing.
“The mitochondrial variability observed in natural populations has never been reproduced in any of the simulations – even in extreme female philopatrios, which suggests that other forces have contributed to the discord,” the authors’ authors conclusionS
“The same approach would be of benefit to other shark species, where early women’s philopathria was based on genetic data.”
The study has been published in PnasS