If you are interested in the evolutionary history of primates, you might wonder which other animals are their closest relatives. You might think of monkeys, apes, lemurs, or even tarsiers, but these are all primates themselves. So, which pair of organisms is most closely related to primates?
The answer might surprise you: it is **flying lemurs** and **treeshrews**. These are two groups of small, furry mammals that live in Southeast Asia and have some remarkable adaptations for life in the trees.
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What are Flying Lemurs and Treeshrews?
Flying lemurs, also known as colugos, are not actually lemurs or even primates. They belong to a separate order called Dermoptera, which contains only two living species: the Sunda flying lemur and the Philippine flying lemur. Despite their name, they do not fly either. They glide from tree to tree using a large membrane of skin that stretches from their neck to their limbs and tail. They feed mainly on leaves, fruits, and flowers.
Treeshrews are also not true shrews or even rodents. They belong to another order called Scandentia, which contains about 20 living species. They are active and agile animals that feed on insects, fruits, seeds, and nectar. They have a long snout, large eyes, and sharp teeth.
How are They Related to Primates?
The reason why flying lemurs and treeshrews are so closely related to primates is because they share a more recent common ancestor with them than with any other group of mammals. This common ancestor was probably a small, nocturnal, arboreal animal that lived in the Cretaceous period.
According to the most recent phylogenetic studies, primates are part of a larger group called Supraprimates or Euarchontoglires, which also includes rodents, rabbits, flying lemurs, and treeshrews. These groups share a common ancestor that lived about 90 million years ago.
Within this group, primates form a sister clade with flying lemurs, meaning that they are each other’s closest relatives. Together, they form another sister clade with treeshrews, meaning that they are more closely related to each other than to any other group within Supraprimates.
Here is a simplified phylogenetic tree that shows the relationships among these groups:
Why is This Important?
Knowing which pair of organisms is most closely related to primates can help us understand how primates evolved and diversified over time. By comparing the features and behaviors of primates with those of flying lemurs and treeshrews, we can infer which traits are ancestral (shared by the common ancestor) and which are derived (evolved later in a specific lineage).
For example, we can infer that the ability to glide using a skin membrane is a derived trait of flying lemurs, since it is not found in primates or treeshrews. We can also infer that the large brain size and complex social behavior of primates are derived traits, since they are not found in flying lemurs or treeshrews.
By studying the genetics and molecular biology of these groups, we can also estimate how long ago they diverged from each other and reconstruct their evolutionary history. For instance, we can estimate that primates and flying lemurs split from each other about 86 million years ago, while primates and treeshrews split from each other about 94 million years ago.
Conclusion
The pair of organisms that is most closely related to primates is flying lemurs and treeshrews. These are two groups of small mammals that live in Southeast Asia and have some remarkable adaptations for life in the trees. They share a common ancestor with primates that lived about 90 million years ago.
By knowing which pair of organisms is most closely related to primates, we can learn more about the evolutionary history and diversity of primates and their relatives.
