A PhD student proved one of Darwin's theories of evolution 140 years after his death

University of Cambridge PhD student Laura van Holstein just proved Darwin's theory -- that a genus with more species also has more subspecies.

(CNN)When Charles Darwin published "On the Origin of Species" in 1859, his evolutionary theories permanently shook up science and the way researchers studied the natural world.

And while his seminal work laid the foundation for evolutionary biology, one major point of his was never proven.
Until now.
    Nearly 140 years after his death, a University of Cambridge researcher has found strong evidence that one of Darwin's hypotheses is true. That hypothesis states that a species belonging to a larger genus should also include more subspecies.
    The graduate student, Laura van Holstein, was able to prove this using a tool Darwin didn't have: Data modeling.
    "I've just reported evidence in favor of a hunch of good old Darwin's," van Holstein, a biological anthropology PhD student at Cambridge and study lead author, told CNN. "I think this has big implications for evolutionary biology."

    Darwin's subspecies theory

    To understand the significance of this development, it's best to start with a refresher on the following taxonomy (or naming conventions): genus, species and subspecies.
    • A genus is a group of animals with similar traits. This can include multiple species. For example, most bears belong to the genus Ursus.
    • A species is a group of similar animals that can interbreed and exchange genes to reproduce. The brown bear is a species under the Ursus umbrella.
    • A subspecies is a group within a species that looks phenotypically different from the rest of the species and has its own breeding range that doesn't overlap with the rest of the species. A grizzly bear is a subspecies of brown bear.
    Darwin predicted that species in a larger genus should also include more subspecies. But he never elaborated on why.
    The evolutionary scientists who followed Darwin suggested that a subspecies represents an early stage of species formation. But that was difficult to prove. After all, evolution takes time.

    She used a tool Darwin never did

    Van Holstein, however, had what those scientists didn't: Data modeling software.
    She wanted to show that the number of subspecies in a species is correlated to the number of species in a genus. If she could prove that, she'd have more evidence to suggest that subspecies are the "raw material" for a new species, she said.
    She ran a few of the models: First, she devised a model using taxonomical information about different species to show that a genus with more species also has more subspecies to prove a relationship.