Furthermore, Mental Floss pointed out that this isn’t just a behavior change, but a change at the genetic level, with natural selection favoring fish that migrate earlier. Salmon are migrating from the ocean to the river two weeks earlier than they did 40 years ago, in response to warmer ocean temperatures. Pink salmon have adapted to migrate earlier because of climate change. When commercial fishing in the 1920s threatened Chinook salmon from Alaska to California, the fish became smaller and shorter-lived, according to Discover Magazine. Salmon have remained resilient, despite several challenges caused by humans. Discover Magazine reported that only 20 generations after the invasive brown lizards arrived, the green lizards developed larger toepads and more scales, which helped them cling to higher branches to avoid competition from the brown lizards on lower branches. When brown anole lizards invaded green anole territory in Florida, the green lizards adapted in just 15 years. Green Anole Lizards Adapted to an Invasive Species The guppies who lived with cichlids matured at an earlier age and produced more babies. The group in the stream without predators were larger, matured later and reproduced slower. In just four years, or six to eight guppy generations, the guppies adapted to their new environments. He moved one group of guppies to a stream without predators to see if they would thrive, and added predatory fish called cichlids to guppy sites that previously didn’t have predators. Resznick wanted to watch evolution happen in real time, so he experimented with changing the predators in guppies’ environment. 5 Animals That Have Evolved Rapidly Guppies Adapted to Predators It turns out that some animals evolve so quickly that researchers can actually observe the changes. This was a pivotal moment in changing the way scientists understand evolutionary biology. However, Discover Magazine reported that in 1981 a researcher named David Reznick demonstrated that you can see animals evolve within a lifetime. Some species evolved rapidly to adapt to major changes in their environment.īack in the 1850s, Darwin had assumed that evolution was a slow, invisible process that could take as many as thousands of generations to produce a new species. The degree and speed of change varies, depending on environmental conditions and the amount of time between generations. But consider animals that have evolved right before our eyes: bugs, fish, birds and more. We often think of evolution as an imperceptible, gradual change over time.
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