Tarsiers are cute little critters with their big, doey eyes and tiny bodies that can fit in the palm of your hand, but they have proven to be something of an anomaly of nature given their bizarre list of traits. Their eyes are twice as big as their brains, they can rotate their heads 180 degrees, track prey using ultrasound and, most unusually for a primate, are completely carnivorous, surviving on insects, small birds, rodents and lizards. They also have an adapted tarsus bone in the ankle (hence the name) that gives them powerful leaping abilities.
All this means that when it comes to positioning the tarsier somewhere within the animal kingdom, biologists have been swaying somewhere between wet-nosed primates, like lemurs, and dry-nosed primates, like moneys and humans. Now a new study published in Nature Communications has finally nailed down an exact spot, and it turns out we have more in common with the miniature mammal than we thought.
Jumping genes
A team of scientists from the Washington University School Of Medicine and the University of Münster in Germany sequenced the complete genome of the tarsier and analysed DNA sequences called transposons, or jumping genes. These transposons can move from one part of the genome to another, duplicating themselves in the process, but over time lose the ability to jump. By seeing which jumping genes were embedded in others, the researchers were able to determine when they lost the ability to jump around and therefore date the different families of transposons.
They then compared the transposon families of tarsiers, humans, dry-nosed squirrel monkeys and wet-nosed bushbabies. The result: only the oldest were shared with bushbabies, meaning the tarsier can finally be classed as a dry-nosed primate like us (and squirrel monkeys).
"Jumping genes help us understand how species diverged from one another over millions of years ago," says Jürgen Schmitz of the University of Münster. "The tarsier genome is a modern archive of evolutionary changes that led to humans."
Tarsiers in trouble
Now that we know we are evolutionarily related to the tarsier, scientists can now use this information to work out why the creature is so unique, and this could be critical to identifying human diseases.
"The tarsier genes that display unique alterations can give us a clue into human diseases involving the same genes," says senior study author Wesley Warren. "If an amino acid has been uniquely changed and it is putatively associated with the tarsier's novel musculature, maybe it's an important part of the protein and worthy of a closer look when linked to human disease."
Unfortunately the number of tarsiers is in decline due to habitat loss and the pet trade, but Warren remains hopeful that the with further DNA study, they will be able to assess the overall health of the population.
"If we can sequence the genome of other tarsiers, we can measure the population diversity… It will help us determine how endangered they really are so we can implement measures to better protect them."