Remembering Peregocetus pacificus — modern whales' otter-like ancestor
The new fossil offers insight into when whales returned to the oceans millions of years ago.
- Researchers discovered a fossil of a four-legged, amphibious whale off the coast of Peru.
- The fossil is among the oldest of its kind at 42.6 million years old, and its skeletal structure offers insights into the transition of whales back into the ocean.
- One of the more exciting findings is that this species suggests that these ancient whales came to South America by swimming across the Atlantic Ocean from Africa and spread across the globe from there.
The evolutionary path of whales has traced a rather circuitous route. First, their ancient ancestors inhabited the oceans, like all life on Earth did. The ocean was a pretty good spot; water provided protection from the sun's rays, there was no concern about drying out, and sources of energy were plentiful. Animals stayed in the oceans for at least 600 million years.
At the earliest, life exited the oceans and adapted to life on land about 500 million years ago, though estimates vary. Eventually, some of this life became part of the clade Laurasiatheria, from which a common ancestor gave rise to giraffes, zebras, hippopotamuses, and — although it seems peculiar — whales. Unlike the other members of their clade, the ancient whale decided that life on dry land wasn't all it cracked up to be and returned to the ocean; there, they eventually lost their legs and grew to become the behemoths we know them as today, though their time on land means they still need to breathe air.
A paper published in Current Biology on April 4 provides a new glimpse into whales' transition back into the oceans. Olivier Lambert and colleagues discovered an exciting fossil of a new species — a four-legged, amphibious whale that the researchers dubbed Peregocetus pacificus. Not only is this new fossil the most complete one of an ancient whale found outside of Indo-Pakistan, it's also the first quadrupedal whale skeleton found in the entire Pacific Ocean. What's more, it's likely one of the oldest such specimens ever discovered — this skeleton is 42.6 million years old.
Unlike the passive giants we're familiar with, P. pacificus didn't leisurely filter krill through baleen. Instead, it's elongated snout and sharp teeth enabled it to prey on relatively large creatures, likely bony fish. But its anatomy suggests an even more interesting life for this species, and it has to do with the species' name, "Peregocetus pacificus," which means "the traveling whale that reached the Pacific Ocean." This is for good reason: P. pacificus got around.
This species of whale was about four meters long and possessed small hooves, meaning it could easily walk on land if need be. Its skeletal structure suggests that it probably swam the way otters do, by undulating its body and tail while simultaneously paddling with its hind limbs.
Its features are similar to those found from other ancient whales in the midst of their transition to the oceans. But these other fossils were found in West Africa, Morocco, and Nigeria, while P. pacificus was found near Peru. What business does this new species have sharing features with fossils found a continent away?
The researchers suspect that P. pacificus was capable of swimming long distances, distances so long that they could cross the Atlantic Ocean from Africa to eastern South America. This would have been an easier feat then than it is today. The two continents during P. pacificus's day were more than two times closer than their modern distance, and the current would have helped them move westward.
From there, P. pacificus probably hugged the South America coastline, traveling north, crossing over Central America (which was underwater during this period, the Middle Eocene), and then moving south again along the South American coast. Ultimately, this particular specimen found its way to the Playa Media Luna in Peru, died, and was dug up 42.6 million years later.
Llambert et al., 2019
This figure shows how ancient whales spread across the globe. The circular dot on the right represents the suspected origin, while the star on the left represents the site where P. pacificus was found. Note the transition from Africa to South America, marked by the roman numeral III.
This finding helps confirm that modern whales once walked on land alongside other ungulates, such as ancient camels and deer. Over time, species like P. pacificus found it better in the oceans. Gradually, they lost hind legs, and their fore legs became flippers. Today, some whales still sport vestigial hind legs concealed inside their bodies. They grew to enormous sizes, lost their teeth, and replaced them with baleen. Seeing P. pacificus's fossil offers us a snapshot of a moment in time 42.6 million years ago, demonstrating the remarkable adaptability of life on Earth.
Behold, the tiny hind limbs (at the left below the tail) of the early whale Dorudon.
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Here's the first evidence to challenge the "fastest sperm" narrative.
Experts argue the jaws of an ancient European ape reveal a key human ancestor.
- The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
- Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
- These fossils may change how we view the evolution of our species.
Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.
A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.
Rethinking humanity's origin story
The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)
As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.
David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.
The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.
Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"
He recently outlined this idea at a conference of the American Association of Physical Anthropologists.
It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.
"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."
Migrating out of Africa
In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.
Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.
The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.
The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.
Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.
Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.
Did we head east or south of Eden?
Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.
Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.
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