Shaking the Family Tree

A 21st-century biochemist puts meat on the bones of Charles Darwin’s 150-year-old discoveries.

Biochemist Douglas Theobald discusses the evolution of molecular structure with doctoral 
student Ashley Lajoie.
Mike Lovett
Biochemist Douglas Theobald discusses the evolution of molecular structure with doctoral 
student Ashley Lajoie.

Like many scientists, Douglas Theobald is prone to cultivating a single patch of scientific ground for long stretches of time. For more than a decade, the assistant professor of biochemistry has been exploring the lush landscape of Charles Darwin’s theory of evolution, an adjunct to his main focus on the evolution of the molecular structure of proteins. It is undeniably well-trodden terrain, with legions of notable minds preceding him on the road to scientific affirmation of the theory of universal common ancestry (UCA) proposed by Darwin in his groundbreaking book “On The Origin of Species.”

“All the organic beings which have ever lived on this earth have descended from some one primordial form,” the English naturalist postulated in his 1859 book, initially generating shock and awe and eventually providing the foundation of modern biology. This idea that all living organisms, from champagne yeast to ladybugs, from oak trees to humans, are distantly related through a shared genetic heritage — what we now call the universal genetic code — has been steadily fortified since Darwin’s time through transitional fossils, as well as in fundamental biological similarities at the molecular level.

The Ascent of Evolution

But if evolution — based on UCA and natural selection as the mechanism of biological adaptation — seems the scientific equivalent of “settled law,” Theobald has given the 19th-century theory some 21st-century ammunition. Earlier this year, the 40-year-old published the first formal, large-scale quantitative test of Darwin’s theory of UCA in the prestigious research journal Nature. The article generated considerable scientific and media interest, as well as the usual frothy denigrations from the evolution-denier camp.

Theobald describes it as a “short, fun study.” But it was also an ambitious undertaking, given that he set out to establish genetic kinship among all life forms going “back across the eons to the emergence of life itself,” as Scientific American put it.

Using probability theory and harnessing powerful computational tools — four Linux computers churned for months at a time — Theobald determined the likelihood that all life evolved from a single common ancestor to be 1 in 10 to the 2,860th power (that’s a 1 followed by 2,860 zeros) more likely than the next most likely scenario of even two common ancestors. He also included a shout-out in his study to creationists. The odds of humans originating independently of all other life forms he determined to be 10 to the 6,000th power (10 followed by 5,999 zeros) to one.

But really, why even bother scaling a statistical Everest when mountains of qualitative evidence, DNA and otherwise, already inescapably support UCA? To answer that question, it helps to know a little about the personal evolution of the Brandeis scientist. The Nature study is the logical outcome of Theobald’s fascination since boyhood with grand scientific ideas. Theobald was one of those kids who actually read the Encyclopedia Britannica from cover to cover. But he didn’t stop there.

The Beagle and the Lab Bench

“I remember being 7 or 8 years old and reading through my dad’s college biology text book on evolution and thinking, ‘this makes a lot of sense,’” says Theobald. His parents, conservative Christians from the Midwest, didn’t share his perspective on evolution or his interest in it. Still, they enthusiastically encouraged the young Theobald to pursue science passionately. By fourth grade, Theobald says, he had essentially taught himself Einstein’s theory of relativity, minus some of the higher mathematics.