UC Berkeley
2017 Stories
A New Story of Birds and Beaks
It’s a familiar story: In a population of birds, beak shapes have been affected by changes in available food sources, and some of these differences are correlated to an increase in fitness providing an example of evolution in action. Only this time, the birds in question aren’t Darwin’s finches and don’t live on the Galápagos Islands. And the change to available food that might be driving the evolution of the birds has nothing to do with droughts or any other natural causes — it has to do with one country’s love of birdfeeders. These new findings, which are in some ways reminiscent of Darwin’s nineteenth-century observations, are based upon decidedly twenty-first century research, combining genomic analysis with ecological data. The result is a new example of rapid evolution occurring in a wild population, literally right in our own back yards.
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Urban Evolution
For a large segment of young people in the United States, the bright lights of the big city represent a real temptation. Continuing a trend that started more than 200 years ago, Americans (and now millenials in particular) are flocking to urban areas. Today more than 80% of Americans live in cities. The draws of this new life seem clear: entertainment, excitement, and opportunity. Of course, city life can also change you in not-so-desirable ways. Urban living has been associated with asthma, allergies, depression, and anxiety. But what about the non-human city dwellers — the bugs and beasties lurking in our metropolitan interstices? How is the hustle and bustle of urban life affecting them?
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The evolution behind an agricultural showdown in Arkansas
This summer, Arkansas put a 120-day ban on the powerful weed killer dicamba after the chemical pitted neighboring farmers against one another. Produced by the agricultural corporation Monsanto, dicamba is meant to be sprayed on fields of soybeans that are genetically modified to resist the herbicide (the special soybean seeds are, of course, also a Monsanto product): the crop survives and the weeds die. Or at least that’s how it was intended to work. Unfortunately, many farmers who hadn’t purchased the herbicide/resistant-seed duo complained that dicamba from neighbors’ fields had drifted onto theirs and damaged their harvest — hence, the temporary ban to give scientists and the company time figure out if the problem was poor spraying technique or the nature of dicamba itself. Dicamba isn’t a new herbicide, but crop seed genetically modified to survive it is — and the extensive use of dicamba that comes with that innovation seems to point to problems with this herbicide. Why are farmers and agricultural companies moving to new weed killer that might be causing unacceptable levels of collateral damage?
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Global change drove the evolution of giants
We live in extraordinary times. The largest animals ever to have lived on Earth happen to be alive today. Blue whales are larger than any mastodon, dinosaur, or mega-toothed shark ever was. They can grow to almost as long as a 737 airplane and weigh about twice as much! And yet, the blue whale is not a freak of nature. They come by their size honestly; they are part of a family of extremely large-bodied filter-feeding whales that includes the gigantic fin whales and Sei whales. Nevertheless, such huge creatures beg the question, why. Why so big? As it happens, this is just the sort of question that studies of evolution can help us answer. Over the summer, while many of us were lounging at the beach contemplating the watery habitat of these massive creatures, scientists announced the results of an investigation into the evolution of body size in baleen whales.
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The bacteria that changed the world
The make-up of Earth’s atmosphere, once the domain of Earth science textbooks, has become an increasingly “hot” news topic in recent decades. As the evidence pointing to human-produced greenhouse gases as the cause of ongoing and future global climate change has mounted, so too has public attention to this threat — most recently manifest in concern over whether the United States will pull out of the Paris climate accord. That accord aims to curb global warming by limiting the greenhouse gases, notably carbon dioxide, that human activity adds to the atmosphere. Atmospheric carbon dioxide levels have increased by more than 40% since the Industrial Revolution. That buildup makes a significant impact on our climate, but overall, carbon dioxide still comprises a small percentage of the atmosphere, less than 0.05%. About 21% of Earth’s atmosphere is oxygen, and most of the rest is nitrogen. But it hasn’t always been so. When life first arose (likely more than four billion years ago), there was no free oxygen in the atmosphere at all. Life was anaerobic, meaning that it did not need oxygen to live and grow. What happened to change the Earth’s atmosphere into one that could support oxygen-loving (and carbon dioxide-generating!) organisms like us? Evolution happened — specifically, the evolution of Cyanobacteria, a group of single-celled, blue-green bacteria.
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Predicting the evolution of polio
In the 1940s and 50s, the polio virus, which mainly affects young children, crippled 35,000 Americans each year. Today, thanks to vaccinations, the disease has been completely eradicated from the United States — and from most of the world’s countries. In 2015, there were just 74 confirmed cases of polio on the entire planet. The virus lives on due to incomplete vaccination, particularly in countries where vaccination efforts have been hindered by poverty and strife. Now new research provides clues about how to prevent some of these rare outbreaks, getting us ever closer to a polio-free world.
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Natural selection hidden in modern medicine?
No one needs to tell a new mother that human childbirth can be challenging, to say the least. While monkeys and apes (our closest evolutionary relatives) spend about two hours laboring during birth, human mothers spend closer to nine hours. And human childbirth is dangerous. In some impoverished areas, for every 100 live births, one mother dies in childbirth and four infants die in the first few days of life. However, access to resources and modern medical interventions, such as C-sections, saves many of those lives. Doctors estimate that 10-20% of births require a C-section for mothers and babies to have the optimal health outcomes. In the United States, one in three babies is born via C-section. Worldwide, C-sections are performed more frequently than any other surgery. C-sections have become so common in some populations that biologists have begun to wonder if the procedure, as it saves lives, could be shaping the course of human evolution…
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Genes from our extinct relatives live on in modern humans
While all humans are remarkably similar at a genetic level — on average any two individuals’ genomes are 99.9% identical — those differences that do exist manifest themselves in the dazzling spectrum of human diversity. From a lithe tribesperson of the Kalahari, to a freckled redhead from Ireland, to a sleek-haired, ruddy-cheeked inhabitant of the Tibetan plateau, Homo sapiens come in many different shapes, sizes, hues, and appearances. While we tend to notice differences that are easy to spot, other “stealth” variations in human populations are not necessarily observable from physical appearance alone. For example, many people of African descent are resistant to infection from malaria, while that trait is much rarer among those who hail from other parts of the world. Now new research into Arctic-dwelling Inuit populations points to a surprising origin for one such “stealth” trait — the ability to tolerate frigid temperatures.
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