Charles Darwin famously marveled at the “endless forms most beautiful & most wonderful” made by evolution, and even, Earth today teems having an estimated 1 trillion species. But just how long achieved it take those species to evolve?
The solution varies widely across lifeforms, “based on taxa [type of creature] and environmental conditions,” Thomas Smith, a professor of ecology and evolutionary biology at the University of California, LA, told Live Science. It ranges from human-observable timescales to tens of an incredible number of years.
Crucially, because evolution happens via inherited changes, a creature’s speed of reproduction, or generation time, limits the rate of which new species can develop referred to as speciation rate based on the University of California, Santa Barbara (opens in new tab) (UCSB). For instance, because bacteria reproduce so quickly, “split[ing] in two every short while or hours,” they are able to evolve into new varieties in years as well as days, based on the American Museum of Natural History (opens in new tab) in NEW YORK.
It could be tricky, however, to find out which bacterial varieties count as new species, Smith said. While scientists delineate species by if they can interbreed, bacteria usually do not reproduce sexually. Nevertheless, a 2008 study in the journal Proceedings of the National Academy of Sciences (opens in new tab) reported a lineage of E. coli (opens in new tab) bacteria observed for many years had evolved the opportunity to use citrate as a food source within an oxygenated environment. As the inability do that is “a defining characteristic ofE. colias a species,” the change could represent the beginnings of a fresh species, researchers said one which developed inside a couple of years.
Plants, in a phenomenon referred to as polyploidy, can duplicate their entire genomes in seeds, leading to additional copies of each chromosome and a fresh species in a single generation. The resulting reproductive isolation “automatically makes a fresh species,” Smith said.
And because many plants reproduce independently, the brand new, polyploid organism can continue to generate more of the brand new species. “Plants tend to be self-fertilizing, so that it can then take up a whole population,” UCSB said.
Even yet in the pet kingdom, speciation can occur on human-observable timescales, particularly among quick-generating insects. Apple maggot flies (Rhagoletis pomonella), for instance, historically fed on hawthorn plants, however, many moved to domesticated apples after these found its way to the Northeast U.S. in the mid-1800s. Since that time, both groups have grown to be reproductively isolated, in accordance with a 2006 study in the journal Annals of the Entomological Society of America (opens in new tab), and so are now considered “host races” step one in a kind of speciation without physical barriers.
Speciation generally moves more slowly in vertebrates but can still happen quickly. A 2017 study in the journal Science (opens in new tab) reported a Galapagos finch immigrated to a fresh island and bred with a native bird, creating a new reproductively isolated lineage within three generations. That lineage may represent the fast initiation of speciation via hybridization of species, as opposed to the slower accumulation of adaptations, study co-author Leif Andersson, a geneticist at Uppsala University in Sweden, told Live Science.
“It is a possible scenario of what sort of new species can develop,” Andersson said. “But how stable it really is over an extended time period is more uncertain.”
The speed record for full speciation among vertebrates likely belongs to cichlid fishes in Africa’s Lake Victoria, Smith said. These fishes exploded into 300 species “from the single founder significantly less than 12,000 years back,” he said. Some research, like a 2000 study in the journal Proceedings of the Royal Society B (opens in new tab), has questioned that timeline, but cichlid speciation “is extraordinary,” Smith said.
To get an upper limit for speciation times, turn to speciation occurring due to physical barriers, Smith said. For example, boas, primarily within the Americas, and pythons, which are native to Africa and Asia, differentiated after SOUTH USA split from Africa. This likely represents tens of millions to 100 million years from continental split to full speciation, Smith said. (These snakes’ last common ancestor slithered roughly 70 million years back through the dinosaur age, in accordance with Australia National University (opens in new tab), while Africa and SOUTH USA split by about 140 million years back.)
Naming the average or most typical speciation time is challenging, Andersson said, but scientists can estimate latest ancestors, giving a rough idea. “In birds and mammals, what we see is that normally a split between well-developed species is similar to a million yrs . old,” he said.
A 2015 study in the journal Molecular Biology and Evolution (opens in new tab) gave another estimate. Drawing on data from a lot more than 50,000 species (though this included few bacteria), the researchers discovered that speciation generally requires the accumulation of mutations over 2 million years. This held true across vertebrates, arthropods (an organization which includes insects, arachnids and crustaceans) and plants.
However, such models require many assumptions, other researchers cautioned in a Quanta Magazine (opens in new tab) story on the study. Scientists are on more solid footing concerning the factors that slow or speed speciation generally namely environmental pressure and reproductive isolation, Smith said. “Across all species the higher the choice pressure and the less gene flow, the much more likely you’ll get speciation,” he said.
Originally published on Live Science.