Charles Darwin was famous for being amazed at the “infinitely beautiful and most wonderful forms” that evolution had produced, and indeed, a land The day is teeming with An estimated 1 trillion species. But how long did it take for these species to evolve?
The answer varies widely with different life forms, “according to Categories [type of creature] and environmental conditions,” Thomas Smith, Professor of Ecology and Evolution biology at the University of California, Los Angeles, for Live Science. They range from human-observable time scales to tens of millions of years.
Crucially, because has evolved It is caused by inherited changes, the speed of a creature’s reproduction, or generation time, which limits the rate at which new species can form – known as the rate of speciation – according to University of California, Santa Barbara (Opens in a new tab) (UCSB). For example, because bacteria multiply rapidly, ‘split[ing] In two minutes every few minutes or hours, “it can develop into new species in years or even days, according to American Museum of Natural History (Opens in a new tab) in New York City.
It can be difficult, however, to determine which bacterial species are considered new, Smith said. While scientists define species by whether they can mate, bacteria do not reproduce sexually. However, a 2008 study in the journal Proceedings of the National Academy of Sciences (Opens in a new tab) I mentioned that the breed of coli bacteria (Opens in a new tab) Bacteria that have been observed for decades have developed the ability to use citrate as a food source in an oxygenated environment. Because not being able to do so is a “characteristic of coli bacteria As a species, “change could represent the beginnings of a new species, the researchers said — one that evolved within a few years.
Plants, in a phenomenon known as polyploidy, can replicate their entire genomes in seeds, resulting in extra copies of each chromosome and a new species in one generation. The resulting reproductive isolation, Smith said, “spontaneously makes a new species.”
Because many plants reproduce on their own, the new polyploid organism can go on to make more new species. “The plants are often self-fertilizing, so they can then form a whole group,” UCSB said.
Even in the animal kingdom, speciation can occur at human-observable time intervals, especially among fast-breeding insects. apple larva (Ragolettes Pomonella), for example, have historically fed on hawthorn plants, but some moved to domesticated apples after arriving in the northeastern United States in the mid-1800s. Since then, the two groups have been isolated from reproduction, according to a 2006 study published in the journal Annals of the American Entomological Society (Opens in a new tab)are now considered “host species” – the first step in a species of speciation without physical barriers.
Speciation generally moves more slowly in vertebrates but can still occur quickly. 2017 study in the journal Sciences (Opens in a new tab) reported that one individual Galapagos finch migrated to a new island and grew up with a local bird, producing a new reproductively isolated strain within three generations. This lineage may represent a very rapid onset of speciation via species crossbreeding, rather than a slow accumulation of adaptations, study co-author Leif Anderson, a geneticist at Uppsala University in Sweden, told Live Science.
“This is a possible scenario for how a new species might form,” Anderson said. “But then how stable it will be over a longer period of time is uncertain.”
Smith said the speed record for complete speciation among vertebrates likely belonged to tilapia fish in Lake Victoria, Africa. These fish exploded into 300 species, he said, “from a single founder less than 12,000 years ago.” Some research, such as a 2000 study in the journal Proceedings of the Royal Society B (Opens in a new tab)He might question this timeline, but the seshidian genres are “unusual,” Smith said.
To find an upper bound on breeding times, Smith said, look at the species that occur due to physical barriers. For example, boas, found primarily in the Americas, and pythons, which are native to Africa and Asia, diverged after the separation of South America from Africa. Smith said this likely represented tens of millions to 100 million years from the continental split to full reproduction. (The last common ancestor of these snakes slithered nearly 70 million years ago during Age of the dinosaursto me Australia National University (Opens in a new tab)while Africa and South America were divided by 140 million years ago.)
Naming the average or most common breeding time is challenging, Anderson said, but scientists can estimate the most recent ancestors, giving a rough idea. “In birds and mammals, what we see is usually … the split between evolved species is up to a million years old,” he said.
2015 study in the journal Molecular biology and evolution (Opens in a new tab) I gave another estimate. Drawing on data from more than 50,000 species (although this includes quite a few bacteria), the researchers found that speciation generally requires an accumulation of mutations over two million years. This was true across vertebrates, arthropods (a group that includes insects, spiders, and crustaceans), and plants.
However, such models require many assumptions, other researchers at A . cautioned Quanta Magazine (Opens in a new tab) Search story. Smith said that scientists are on more solid grounds for the factors that slow or speed up speciation in general — environmental pressure and reproductive isolation. “Across all species…the more selection pressure and less gene flow, the more likely you are to get new species,” he said.
Originally published on Live Science.