2014 Stories
New fossils are no “missing link”
Last month, scientists announced the discovery of 55-million-year-old fossils that belonged to a mammal from ancient India, Cambaytherium thewissi. The hoofed animal may not have been particularly distinctive looking — it would have weighed between 45 and 75 pounds, resembling a cross between a wild boar and a tapir — but it does occupy a distinctive place on the Tree of Life. Some news outlets immediately began heralding the discovery as a “missing evolutionary link” between horses and rhinos, or their common ancestor. As it turns out, neither is true…
Read more »Evolving an invasive species
Imagine a quintessential scene from a Golden State vacation: standing on the bluffs off Highway One, taking in a view of the beach below and a Pacific sunset on the horizon. It’s classic California. Only what’s beneath your feet on that cliff is not Californian at all. The succulent highway iceplant (Mesembryanthemum crystallinum), a native of South Africa, was first introduced to California in the early 1900s and has since spread up and down the coast, competing with native plants for resources and suppressing the growth of native seedlings. And it’s not just California. Invasive species cause serious environmental disturbances all over the world: introduced pythons threaten native wildlife in the Everglades, invasive plants have changed regions of South Africa from grassland to scrub, foreign barnacles displace mussels and oysters on Europe’s northwestern coasts. In the U.S. alone, invasive species cause billions of dollars of damage each year and contribute to the threat faced by hundreds of endangered species. But what makes an invasive species in the first place? Plenty of organisms make it to new ground, but many just can’t hack it and die out or remain marginal, while other species take over. Biologists have proposed many hypotheses to explain the difference, but now new research (based on a very old idea!) suggests that evolution can help us predict which introduced species are more likely to become problematic invasives.
Read more »Ebola and evolution
The Ebola outbreak in West Africa has international medical organizations on high alert and people all around the world antsy — even those who live in the Americas and Australia, oceans away from the disease’s epicenter. The disease is normally carried by animals like fruit bats, but occasionally makes the jump to humans, and when it does, it is deadly, killing more than half of those infected. However, because it is only spread by direct contact with bodily fluids, most of the world need not fear for their lives. In recent months, some media outlets, and even a scientist or two, have begun to wonder aloud whether the Ebola virus could “mutate” and become airborne — but of course, what is actually meant is whether the virus can evolve in ways that allow it to be passed along more easily, just as the flu can be spread by a sneeze. Here we’ll unpack the question of Ebola’s evolution a little further and see why this outcome is unlikely.
Read more »Evolution accounts for taste
Most of us get in line at the ice cream shop or tear into a piece of chocolate cake without giving much thought to why we like what we do. Humans appreciate a wide variety of tastes because of our omnivorous evolutionary history and the genes we carry that allow us to sense sweet, salty, sour, bitter, and umami (i.e., savory) flavors. But the same isn’t true of all animals. Most cats, for example, dubiously sniff at sweets. This is because, over the course of its evolutionary history, the feline lineage lost a functional gene to detect sweet flavors. Birds also lack this gene and, usually, the sweet tooth that comes with it — but there are a few notable exceptions. Hummingbirds, for example, make a proverbial beeline for honey-sweet liquids. Why are hummingbirds sugar junkies, while robins stick with worms? New research reveals at a genetic level the evolutionary changes that account for such diverse tastes.
Read more »Why the Y is here to stay
The Y chromosome is finally getting the respect it deserves. Since the early 1900s, we’ve known that the Y chromosome is responsible for making males—XX embryos develop into girls and XY embryos develop into boys—but the Y was thought to do little else. After all, at just one quarter the length of the X chromosome, the Y is relatively puny. Biologists hypothesized that the few genes it does carry contribute to processes like sperm production and testes development by helping turn on and off other genes. In fact, the Y had such a bad rap that many researchers suggested that it was on its way to evolutionary extinction. However, now, new research suggests that the Y chromosome is here to stay. Its function goes far beyond triggering maleness…
Read more »Genetic engineering vs. evolution
In the late 1990s, a new weapon in the fight against agricultural pests was introduced: Bt corn. The new maize variety was genetically engineered to carry genes from the bacterium Bacillus thurinigiensis (hence the moniker “Bt”) that cause the crop to produce an all-natural pesticide. This meant that growers could get good yields from their cornfields without spraying on so many toxins. Since then, many farmers have jumped on this bandwagon. In 2012, more than 69 million hectares were planted with Bt crops — an area about the size of Texas! There has been much debate over the risks of this technological advance, but now it appears that the downfall of Bt corn might be the very problem that it was supposed to solve in the first place: agricultural pests, in particular the western corn rootworm. These beetle larvae eat the roots of corn plants potentially ruining the crop. In recent years, more and more larvae that are resistant to the effects of the Bt toxin have been showing up in fields and chewing their way into plants. How and why did this happen? It all comes down to evolution.
Read more »Evolutionary history is more than skin deep
Many of the marks that evolutionary history has left on our bodies are invisible. Lactose tolerance, a predisposition towards diabetes, genes that contribute to breast cancer, and many other inconspicuous traits are legacies of the paths that our ancestors took as they left or stayed in Africa between 60 and 125 thousand years ago. However, other markers of these unique evolutionary histories are perfectly obvious, perhaps most notably skin color. It’s clear that people whose ancestors hail from different parts of the earth have differently colored skin and that this is related to how much of the sun’s radiation hits that part of the planet. The less radiation, the lighter the native population‘s skin color tends to be. This is a great example of recent evolution in human populations. But what if we go back deeper in our evolutionary history, back to when all of humanity lived in Africa? At that time, all humans had darkly pigmented skin. A new study sheds light on how and why this skin pigmentation evolved.
Read more »The deep roots of diabetes
The modern diabetes epidemic is caused, not by a virulent pathogen, but by the spread of an even stealthier invader: the Western lifestyle. As people around the world have begun to eat less healthily, lead more sedentary lives, and live to older ages, adult onset diabetes (type 2 diabetes) has become common in places where the disease was previously unknown. Between 1985 and 2002, the number of people with diabetes grew from 30 million to 217 million, and this figure is expected to exceed 366 million by 2030. But the epidemic has not been even-handed. Even accounting for differences in lifestyle, some populations have been hit particularly hard. Mexicans and Latin Americans, for example, have nearly twice the chance of developing diabetes that non-Hispanic white Americans do. New research addresses these disparities. Last month, scientists announced that they’d discovered a gene that helps explain the difference in diabetes risk among many populations. In a strange twist, the gene version in question traces its ancestry back to Neanderthals! What exactly is going on here?
Read more »