![]() ![]() It’s impossible to measure the full number since scientists haven’t identified all species on Earth, but we’re estimated to lose 1,000 to 10,000 times the normal number of species to extinction.īut it’s possible that within that flood of extinctions, there might be a number of species learning to rapidly adapt and survive.Ĭonsider a 2015 study that followed robot “species” in a computer simulation of evolution. And those are just some of the few we know about. In the past 15 years, we’ve lost numerous species, including the Hawaiian Po’ouli (or Black-faced Honeycreeper), the West African black rhinoceros, Spix’s Macaw and the Madeiran Large White Butterfly. Why some survive while others don’t is a crucial question in the age of the Anthropocene, the Earth’s sixth great extinction. The limnetic (top) and benthic (bottom) stickleback. Three distinct species of finch on the island of Floreana were observed in 1947, but since then researchers have found only two species, and the genetic evidence points to reverse speciation.Īs with the case of the sticklebacks of Enos Lake, these examples show human activity is driving hybridization around the world-whether we’re aware of it or not. Then there are Darwin’s famous Galapagos finches. The mallards now account for more than 80 percent of New Zealand’s dabbling duck population, and as they continue to breed with grey ducks, the latter comes ever closer to extinction. Examples of this kind of hybridization abound: The endemic grey ducks of New Zealand are threatened with extinction not only from habitat loss, but also because of interbreeding with invasive mallard duck species. Today some researchers say that reverse speciation may be becoming more common-especially in environments altered by humans. It’s obvious truth even if it seems contradictory: the same selective pressures that drive some species to extinction force others to adapt and evolve. “So profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being and as we do not see the cause we invent cataclysms to destroy the world, or invent laws on the duration of the forms of life!” he wrote. Quite the contrary: Extinction was a fundamental part of the theory that Charles Darwin, the grandfather of evolution, put forth in 1861 in his seminal Origin of Species. Though it may sound counterintuitive, evolution and extinction aren’t mutually exclusive. It’s really hard to say if they’re going all the way back, but it might be following that path.” “Their ecological role is slightly shifted from the earlier species. “Whether they went back to being an ancestral species is debatable,” Rudman says. With the sticklebacks, it still isn’t clear whether the new species is the same as the common ancestor that both evolved from, or something wholly different. Just because two become one, doesn’t mean it’s the same species that you started out with. Reverse speciation is when those distinct species come together again, until they become one species yet again.īut the process isn’t as simple as it sounds. The most well-known example is Darwin’s finches: Over time, finches on different, isolated islands diverged in beak size and other qualities until they became distinct species. Regular speciation happens when members of one species are divided by changes in their habitat or behavior. What happened with the finger-length fishes is an example of “introgressive extinction,” otherwise known as reverse speciation. ![]() You might be saying to yourself: Wait, that’s not how evolution works. “The crayfish physically altered the way the sticklebacks nest and breed, which increased the probability of mating” between the two species, he says. “It seems like someone may have introduced the crayfish possibly as a food source,” says Seth Rudman, an evolutionary biologist at the University of British Columbia whose paper on the phenomenon came out in Current Biology earlier this year. Within three years of the crayfishes’ arrival, the two species had once again merged. The answer had to do with invasive crayfish, which were likely introduced into the lake ecosystem by humans. And all was well.īut then something strange happened: The two species of fish once again became one. Their habitats and behaviors were so different that they rarely met, and never interbred. The former stayed near the floor, where they fed on bottom-dwellers the latter swam up near the sun, eating insects at the surface. For thousands of years, two distinct species of these spiny silver sea creatures-known as the benthic sticklebacks and the limnetic sticklebacks, both descended from a single species-lived in peaceful coexistence. ![]() Seuss book, that’s what actually happened to the threespine stickleback fishes of Canada’s Enos Lake. Though it might sound like the plotline of a Dr. ![]()
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