Evolutionary trees of organisms determined by comparing anatomy rather than gene sequences could be misleading, new research led by scientists from the Milner Centre for Evolution at the University of Bath in the United Kingdom. The study describing the findings was recently published in the journal Communications Biology.
The new study shows that researchers often need to overturn centuries of scholarly work that classified living things according to how they look.
Biologists have been reconstructing the "family trees" of animals by carefully examining differences in their anatomy and structure, called morphology in scientific terms, since the 19th century.
How Is Genetic Data Beneficial To Biologists?
However, biologists are now able to use genetic or molecular data to help piece together evolutionary relationships for species very quickly and cheaply, because rapid genetic sequencing techniques have been developed. When trees are reconstructed using these techniques, organisms that were once thought to be closely related are observed to belong to completely different branches of the evolutionary tree.
Evolutionary Trees Based On Morphology Compared With Those Based On Molecular Data
In a first, the scientists at Bath compared evolutionary trees based on morphology with those based on molecular data, and mapped them according to geographical location, the study said. The researchers found that the animals grouped together by molecular trees lived more closely together geographically than the animal groups using the morphological trees.
In a statement released by University of Bath, Matthew Wills, one of the authors in the paper, said that it turns out lots of our evolutionary trees are wrong. He added that for over a hundred years, biologists have been classifying organisms according to how they look and are put together anatomically, but molecular data often tells us a rather different story.
Wills said the study proves statistically that if one builds an evolutionary tree of animals based on their molecular data, it often fits much better with the animals' geographical distribution.
Biogeography Is An Important Source Of Evolutionary Evidence
The biogeography, which is where things live, is an important source of evolutionary evidence that was familiar to Charles Darwin and his contemporaries, Wills said.
For instance, tiny elephant shrews, aardvarks, elephants, golden moles and swimming manatees have all come from the same big branch of mammal evolution, despite the fact that they look completely different from one another and live in very different ways, Wills explained.
Molecular trees have put those animals all together in a group called Afrotheria, so-called because they all come from the African continent. The group matches the biogeography of the animals, Wills said.
Convergent Evolution Is Much More Common Than Biologist Previously Thought
According to the study, convergent evolution, which occurs when a characteristic evolved separately in two genetically unrelated groups of organisms, is much more common than biologists previously thought.
Wills also said that there are lots of famous examples of convergent evolution, such as flight evolving separately in birds, bats and insects, or complex camera eyes evolving separately in squid and humans.
However, biologists can now see with molecular data that convergent evolution happens all the time, Wills said. Certain things which researchers thought were closely related often turn out to be far apart on the tree of life.
Wills further said that people who make a living as lookalikes are not usually related to the celebrities they are impersonating, and individuals within a family do not always look similar. It is the same with evolutionary trees too, Wills explained.
He said this proves that evolution has been fooling everyone, including the cleverest evolutionary biologists and anatomists, for over 100 years.
What Prompted Darwin To Develop His Theory Of Evolution?
Dr Jack Oyston, the first author on the paper, said the idea that biogeography can reflect evolutionary history was a large part of what prompted Darwin to develop his theory of evolution through natural selection. Therefore, it is pretty surprising that it had not really been considered directly as a way of testing the accuracy of evolutionary trees in this way before now, Oyston added.
Researchers have found strong statistical proof of molecular trees fitting better not just in groups like Afrotheria, but across the trees of life in birds, reptiles, insects, and plants too. This is something Oyston considers most exciting.
Oyston said this being such a widespread pattern makes it much more potentially useful as a general test of different evolutionary trees.