General Question

LostInParadise's avatar

What role does chance play in the extinction of species?

Asked by LostInParadise (28948points) April 7th, 2012

I understand that evolution plays a role, either because a species evolves into something better adapted or fails to compete against another such species. I also understand that catastrophic events play a role, whether asteroid collision or human encroachment.

I have read that extinction rates on islands are greater than elsewhere. The reason given is the greater chance of a sequence of unfortunate events wreaking havoc on a necessarily smaller population. How big a factor are such events in general?

In most cases, plants and animals live in a delicate balance with their surroundings. They reproduce up to a certain carrying capacity and then go through cycles of population increase and decrease. Is it reasonable to say that by pure chance there will eventually be an unfortunate combination of circumstances that will push a species over the edge into extinction?

Please do not interpret this question in political terms. I am by no means making a case against the preservation of endangered species. I am just wondering if the precariousness of life must eventually catch up to all species.

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11 Answers

CaptainHarley's avatar

A rather extensive one, I would think. Meteor impacts, geological events, dissapearance of habitat, emergence of a new predator… the list seems extensive.

gasman's avatar

Extinction need not be caused by cataclysmic events. More commonly a species might gradually become extinct as its food sources – also living species – evolve to become less available; or as its habitat gradually disappears over millennia; etc. It’s a rare species that can adapt and survive through several geologic ages.

The role of chance is huge, both for emergence of new species as well as extinction of existing ones. The lesson of evolution is randomness and lack of any grand plan or purpose.

Keep_on_running's avatar

It can play quite a large role. For example, the Tasmanian devil could have started out with just one or two of the animals infected by chance with facial tumour disease. Which then quickly spread and resulted in them being placed on the endangered species list. Without human intervention, they could very well be extinct by now.

Coloma's avatar

Sudden disease outbreak can decimate a species, as it can humanity as well. Many of the deer in my area have had some sort of mange like disease the last few years. Local biologists don’t really know whats going on. I just had a doe staggering across my yard a few days ago, trying to keep up with a little roving band of other deer. She was emaciated and her coat was horrible. I think disease is a factor for sure along with everything else mentioned.

flutherother's avatar

It is all down to chance. If it wasn’t for the Chicxulub impact we would not be here and the dinosaurs would still dominate the planet.

CWOTUS's avatar

Until mankind came along and started to do things with “intent”, wasn’t it always and only chance that determined species’ survival? No other species other than man has ever “intended” to wipe out (or preserve) any species until now.

mazingerz88's avatar

Everything. As with extinction as much as with creation.

Response moderated
Earthgirl's avatar

Rarebear That was a bad link. Is this what you wanted to link to?

Bill1939's avatar

I imagine that climate change played a significant role in driving changes in species. For example, evidence of the existence of a large feathered dinosaur in China was recently reported. It was suggested that this adaptation enabled them to survive longer than other dinosaurs as glaciation slowly approached.

The effect of solar flares during periods when the Earth’s magnetic field had collapsed, such as while reversing, could produce random changes in the DNA of life forms, some of which might have facilitated the survivability of new species. Bacteria and viruses can also effect genomes, resulting in changes leading to adaptation or extinction.

I think it reasonable that chance is involved in combining circumstances that will push a species unable to adapt into extinction.

Rarebear's avatar

@Earthgirl Yep. Thanks. Not sure why my link didn’t work. I’ll flag my response.

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