Is this the ancestor we share with Fido and Fluffy? First picture of shrew-like creature which evolved 200,000 years after the dinosaurs were wiped out
- Creature evolved 200,000 years after the dinosaurs were wiped out
- Research confirms earlier theory
This is the first picture of the small creature with a long tail and a taste for insects that could be the common ancestor we share with all placental mammal, say scientists.
And previous theories about when that ancestor emerged could be wrong.
Now it seems that those distant ancestors didn't appear until after the dinosaurs were wiped out, reveals a new study.
Ancestor: This is the shrew-like mammal with a long tail and a taste for insects that could be the ancestor of many of the mammals on Earth today, from cats and dogs right up to whales
The research traced the origin of placental mammals - a diverse group, which includes animals ranging from rodents to whales to humans - to a common ancestor, described as a small little insect eating animal.
The shrew-like creature weighed less than half a pound, had a long tail, and ate insects.
It evolved some 200,000 years after a massive asteroid impact led to the extinction of the dinosaurs 65 million years ago.
From this small beginning sprang every 'placental' mammal that gives birth to mature live young, including dogs, cats, rodents, whales and humans.
Placental mammals are the largest branch of the mammalian family tree, with more than 5,100 living species. Non-placental mammals consist of kangaroos and other marsupials, and egg-laying monotremes such as the duck billed platypus.
WHAT WIPED OUT THE DINOSAURS?
All non-avian dinosaurs as well as many groups of birds suddenly became extinct approximately 66 million years ago.
Many other groups of animals also became extinct at this time, including ammonites (nautilus-like mollusks), mosasaurs, plesiosaurs, pterosaurs and many groups of mammals.
This mass extinction is known as the Cretaceous–Paleogene extinction event, which is thought to have been caused by a huge asteroid striking the Earth in Mexico.
The nature of the event that caused this mass extinction has been extensively studied since the 1970s; at present, several related theories are supported by paleontologists.
Though the consensus is that an impact event was the primary cause of dinosaur extinction, some scientists cite other possible causes, or support the idea that a confluence of several factors was responsible for the sudden disappearance of dinosaurs from the fossil record.
But contradicting a widely held theory, the study concluded that this ancestor didn't start splitting into present day lineages until after the extinction event which wiped out dinosaurs - as well as 70 per cent of all species on Earth - some 65 million years ago.
Instead, the American Museum of Natural History study found there was an explosion in placental mammals following this earth-changing event, known as the Cretaceous-Paleogene (KPg) extinction.
It is now thought the original ancestor began speciating 200,000 to 400,000 years after the event.
'This is about 36 million years later than the prediction based on purely genetic data,' said Marcelo Weksler, an author and research associate in the Museum's Department of Mammalogy in Brazil.
Using the world's largest dataset of both genetic and physical traits, the international team of scientists built a new 'tree of life' for placental mammal, using phylophenomics.
They reconstructed the anatomy of the common ancestor by mapping traits on to the evolutionary tree, using a powerful cloud-based and publicly accessible database called MorphoBank.
Using this method, the scientists concluded that the common ancestor had features such as a two-horned uterus, a brain with a convoluted cerebral cortex, and a placenta in which the maternal blood came in close contact with the membranes surrounding the fetus, as in humans.
The Science article is the result of a multi-year collaborative project funded by the National Science Foundation's Assembling the Tree of Life program.
Lead author Maureen O'Leary, an associate professor in the Department of Anatomical Sciences in the School of Medicine at Stony Brook University, said: 'Species like rodents and primates did not share the Earth with non-avian dinosaurs but arose from a common ancestor - a small, insect-eating, scampering animal-shortly after the dinosaurs' demise.'
The evolutionary history of placental mammals has been interpreted in very different ways depending on the data analysed.
One leading analysis, based just on genomic data, predicted that a number of placental mammal lineages existed in the Late Cretaceous and survived the Cretaceous-Paleogene extinction.
Other analyses place the start of placental mammals around this time and still others set their origin after this event.
But by using two types of data including both phenomic, which includes observations of traits such as anatomy and behaviour and also genomic data encoded by DNA, the recent study was made much more robust, author Michael Novacek said.
Mr O'Leary added: 'Discovering the tree of life is like piecing together a crime scene-it is a story that happened in the past that you can't repeat.'
'Just like with a crime scene, the new tools of DNA add important information, but so do other physical clues like a body or, in the scientific realm, fossils, and anatomy.
'Combining all the evidence produces the most informed reconstruction of a past event.'
Nancy Simmons, paper author and a curator in the Department of Mammalogy at the American Museum of Natural History, said the study was extremely useful when studying such a diverse group of species.
'There are over 5,100 living placental species and they exhibit enormous diversity, varying greatly in size, locomotor ability, and brain size.
'Given this diversity, it's of great interest to know when and how this clade first began evolving and diversifying.' The findings were published in the journal Science.
Cats are just one of the more than 5,100 living placental species that evolved from the common ancestor