Oxygen is responsible for the Cambrian Explosion? Maybe not.

Approximately 540 million years ago, life rapidly diversified in an evolutionary burst — a biological “Big Bang” that witnessed the emergence of nearly every modern animal group. Scientists have long sought to determine what caused the Cambrian explosion, and to explain why animal life didn’t take this step at any point about a billion years earlier. (Please note: “explosion” indicates things happened rapidly! Ask a paleontologist what “rapidly” means and you’ll notice you may need to redefine your idea of “explosion”)

“The most popular narrative puts oxygen front and center. The geological record shows a clear link, albeit an often subtle and complicated one, between rises in oxygen levels and early animal evolution. As Quanta reported earlier this month, many researchers argue that this suggests low oxygen availability had been holding greater complexity at bay — that greater amounts of oxygen were needed for energy-demanding processes like movement, predation and the development of novel body plans with intricate morphologies.

“It’s a very attractive, intuitive explanation,” said Nicholas Butterfield, a paleobiologist at the University of Cambridge. “And it’s wrong.””

Want to know what I love most about paleontologists? They are so unabashedly willing to argue (to the death!) small points with very little data. It is fascinating, and worth reading about this oxygen vs. complexity saga here.

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Watching a new species evolve

Biologist who study experimental evolution will tell you that they get to see species evolve all the time. However, for the first time, scientists have been able to see the evolution of a completely new species, in the wild, in real-time. And it’s not something rapidly evolving like bacteria.

It’s a new species of Darwin’s finch, endemic to a small island in the Galápagos, Daphne Major. And it evolved in just two generations.

Read about this awesome study, and gather fodder for that argument that “evolution isn’t true” that you might be having over your Thanksgiving weekend, here!

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The Underground mosquito

Not underground as in it burrows into the earth, but the formal noun referring to the London Underground. That’s right, as well as being an exceptional form of public transportation, the London Underground has it’s very own species of mosquito.

It was first reported during World War Two, when the tunnels of the Underground were used as overnight shelters, housing 180,000 people.

And then it was largely forgotten until a doctoral student, Katharine Byrne, started studying this subterranean pest. And found that the Underground mosquito is no longer able to interbreed with other mosquitoes:

“There are differences in both the mating behaviour and the reproductive biology,”

David Reznick

Read about it over at BBC, or read the original paper here!

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Preventing Flies from Interbreeding

“Pour some cold cream into a cup of hot, black coffee, and you end up with a drink that’s midway between the two ingredients in color, temperature, and flavor. A similar kind of blending can occur if members of closely related species frequently mate with each other, but many species have mechanisms to prevent such mixing.” -HHMI News

My new favorite analogy about species inbreeding, and one that every academic can relate to.

But seriously, over at Howard Hughes Medical Institute Jay Shendure and Harmit Malik (a researcher I have long admired) has come up with a clever series of experiments to find the gene responsible for keeping two fly species separate.

Read about their new technique here!

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Alvin, Simon and Theodosius Dobzhansky*

You know the type. Big, brown eyes. Cute, little nose. Long, striped tail.

Tamias amoenus canicaudus, Steptoe Butte, WA, photo: Noah M Reid

Tamias amoenus canicaudus, Steptoe Butte, WA, photo: Noah M Reid

Chipmunks are adorable and one of the more easily viewed yet still kind of exotic North American mammals (in my opinion). I worked on red-tailed chipmunks for my Master’s degree at the University of Idaho with Jack Sullivan. Sullivan (et al.) just published a review of all the chipmunk research that’s taken place in his lab over the past 10 years or so. Central to the review is the concept of divergence with gene flow (DGF), but let’s start with some back story.

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Missed Connections: reproductive isolation and diversification rate

MissedConnections“You: on the earth’s surface. so young. so dynamic. full of life and suggesting a world of possibility. Me: subterranean. really old. fossilized, almost. intriguing but slightly inscrutable. We brushed past each other in Rabosky and Matute (2013). I thought there was something there, but in the blink of a p-value you were gone.” 

One of the perennial questions in evolutionary biology is “What factors determine how many species are on earth?” Researchers take numerous approaches to get at this very big question. One is to look for correlations between attributes of organisms, the environments they inhabit, or geologic history and rates of species diversification. This the study of macroevolution, and it is based on the idea that the discovery of these correlations on large scales (often using datasets with hundreds to thousands of species with deep histories spanning tens of millions of years) would be a powerful indicator of the factors governing species richness. Another approach is to study speciation on a small scale, to examine sets of closely related populations currently in the process of diverging. The thought is that if we can observe the forces driving divergence in contemporary populations, we can use those observations to develop a more general understanding.

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