is evolutionary change faster in local populations?
as long as widely separated populations remain the same species, the only evolutionary change in the species as a whole must be due to mutations that are advantageous throughout the species, in all the environment it inhabits. since there must be few such mutations, evolutionary change must necessarily be slower in widespread species than in isolated local populations.
- Cal KingLv 72 years agoFavorite Answer
Yes, local populations are adapted to local environments, so they are more likely to change. Many scientists suggest that new species most often arise from a small local population adapting to a new environment. An entire species transforming into a new species is considered a lot less likely. Indeed if we look at the evolutionary history of humans, we see that our ape ancestors were driven into the new environment of the savanna before they changed into australopithecines. Apes continue to occupy forests and they remain relatively unchanged. If we compare the gorilla and chimp to the orangutan for example, The African apes are a lot more similar to the Asian apes than they are to humans even though they last shared an ancestor with us more recently than they do with the orangutan.
The Neanderthals evolved from a small local population of Homo erectus in Europe. Homo sapiens also did not evolve in Africa until Homo erectus was nearing its end in Africa. That suggests that it is often necessary for a large population to undergo a drastic reduction in size (a population crash, for example, because of a severe drought and food shortage) for a new species to evolve from the remaining individuals, because genetic changes can often be swamped in a large population.
Keep in mind however that the ultimate driving force of evolutionary change is not isolation or the size of the parental population, but adaptation to new niches. if a few individuals have adapted to a new niche, and if they are able to isolate themselves reproductively (e.g. by evolving premating isolation such as a new mating dance, a new song, or new color patterns) then these individuals can evolve into a new species even though there is no geographic isolation between them and individuals of their parental species. Scientists call this sort of speciation sympatric speciation, and it is a lot more common than many scientists believe. Indeed, even though nothing really separates a forest from the savanna, our ancestors could evolve because they no longer go back to the forests and mate with apes, because they were acting a lot differently than apes just to survive in the new environment. They were already walking upright and they may have lost their body hair quite early to adapt to the new hotter environment. A hairless ape walking on two legs (even though anatomically it was still a quadruped) would not look like the same species to a hariy ape living inside a forest. It would therefore be fairly easy for them to avoid mating with each other. Besides, any hybrid from such a mating would likely be ill adapted to either group. A hairless ape inside a forest is going to get chilled easily, and a hairy ape living in the savanna is going to suffer heat strokes more easily. When hybrids are ill adapted, then their parents are unfit (leave fewer descendants or none at all). Natural selection would therefore eliminate them, and the likelihood of future interbreeding is reduced, leading to the evolution of a new species rapidly.
Because the ultimate driving force of evolution is adaptation to local environments. Two or more populations that have been isolated from one another for a long time may not change and they remain the same species. This point is often not understood by some biologists, who mistakenly believe that isolation will almost certainly lead to the appearance of evolutionary changes and new species, and they also think that speciation without isolation is improbable. They are wrong on both counts. New species can arise sympatrically if some individuals adapt to a new niche (such as eating a new kind of food and evolving a new beak to process the food better, e.g. Darwin's finches), and new species may not evolve even if there is geographic isolation for long periods of time. The theory of Punctuated Equilibrium in fact states that a species changes little over its entire lifetime because most changes would make them less well adapted to their niches. if they adapt to a new niche, then changes can be rapid, or punctuational, and the result is a new species.
In layman's terms Punctuated Equilibrium means don't fix what ain't broke, but fix it quickly if it breaks.
- Anonymous2 years ago
"the only evolutionary change in the species as a whole must be due to mutations that are advantageous throughout the species"
[There's also sexual selection and random genetic drift. Natural selection isn't the only evolutionary mechanism.]
"evolutionary change must necessarily be slower in widespread species than in isolated local populations"
Yes, that's true. The mutations spread through small populations faster.
- Gray BoldLv 72 years ago
Yes. Punctuated equilibrium is a theory in evolutionary biology which proposes that once species appear in the fossil record they will become stable, showing little evolutionary change for most of their geological history. This state is called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis. Cladogenesis is an evolutionary splitting event where a parent species splits into two distinct species, forming a clade. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, opening up ecological niches for the survivors. The events that cause these species to originally separate from each other over distant areas may still allow both of the species to have equal chances of surviving, reproducing, and even evolving to better suit their environments while still being two distinct species.Source(s): https://en.wikipedia.org/wiki/Punctuated_equilibri... https://en.wikipedia.org/wiki/Cladogenesis
- Daniel RLv 62 years ago
But the problem is your initial caveat: "as long as widely separated populations remain the same species". Why would they? Evolutionary change is precisely that of separated populations splitting into separate species.
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- 2 years ago
There is no such thing as evolution.