and that’s why we still have fish…

June 11, 2010

Chances are that somewhere right now, a creationist is bitterly trying to prove that evolution is wrong and that the fossil record doesn’t actually provide any evidence for the theory because it won’t show how one species becomes another. Then, after either thinking that he’s triumphantly defeated modern biology or sighing heavily because those evolutionist heathens won’t heed his wise words, he leaves science writers and scientists to deal with his assertion. And here’s the funny part. Our creationist in question is absolutely right. Fossils don’t show how one species becomes another. If they did, then much of what we know about evolution would have to be drastically revised to explain how a species could suddenly change its distinguishing features. To show how biologists today explain the flow of evolution, here again is David Attenborough for the BBC’s Tree of Life.

Creationists heavily rely on the notion of separating all life into a neat, tidy box they label as kinds and we tend to label as species. The most progressive ones may even accept that within any particular species there is a level of genetic churn and outward change. But what they don’t understand, or don’t want to understand, is the nature of how we label living things. Our taxonomy is fairly arbitrary and when we really start digging down to a bone by bone analysis of the fossil record, we find a lot of overlap, and incomplete segments become hard to classify because they could belong to multiple species. That’s because in nature, species are related and as time goes on, the offspring of species A can accumulate so many genetic changes and settle in environments so inhospitable to their ancestors that they interbreed, increase the number of genetic changes they have, and eventually, their progeny could be classified as species B in a few million years or so, as the mutations keep on building with each generation even more removed from the population that gave birth to their parents.

And eventually, as their genetic changes accumulate thanks to natural selection, they’ll keep mating with each other and if they’re good enough survivors, they may even spawn species C, which will continue to repeat the cycle of speciation as long as the habitat permits it. Here’s an example of this speciation going on right now in the Arctic. Zoologists had a pretty good idea that polar bears and grizzlies were evolutionary relatives, sharing a distant ancestor which gave rise to a species well suited to hunt and forage in forests, and another that was able to live in the icy plains, hunting for seals. Normally, the two want nothing to do with each other and grizzly bears normally try to scare away any polar bear that comes too close to their territories. But today, as grizzlies are venturing further north, they’re not just bumping into polar bears for a growling contest. Instead, the bears are mating and producing huge, powerful offspring known as grolars. And should the grolars survive over a long enough period of time and start interbreeding, they’ll become a new species. Once again, nature shows how genetic mutations and natural selection shape life on our planet and how instead of one species turning into another, speciation relies on one species becoming two, and maybe even three.

So how does a creationist expect rare, often incomplete fossils to show how one species turns into another, or how that change happens when speciation requires new species branching off from established ones? If nature worked the way creationists think, Tiktaalik and well, every other fish would have to be part of one and the same species and be walking on land as amphibians, rather than just father the ancestors of amphibians which emerged out of the water and fathered the ancestors of reptiles. According to the theory of evolution, the original species can stick around for as long, or even longer then their novel descendant. That’s why there are still fish in the oceans (although not the same fish we had 400 million years ago), and modern Tiktaaliks are still appearing. According to the creationists’ quasi-Lamarckian view of evolution, that’s not how nature has to work and since they see themselves as the pinnacle of life on Earth, they’ll demand that biologists show them how a “lower form of life becomes a higher form,” a meaningless, pseudoscientific notion of those who got their idea of evolution almost solely from Rudolph Zallinger’s March of Progress.

So the next time creationist zealots devoted to disproving evolutionary science ask you to provide evidence for speciation as they believe it happens, you’ll know you’re dealing with someone who hasn’t the faintest clue of what he’s talking about, so much so that he’s arguing against potential evidence that would be a major shock to modern biologists and put some of the core concepts behind evolutionary theory into question. And if you’re the kind of creationist who likes to use this throwback to Lamarckism, you should now know that you’ve been trying to prove to people that gravity doesn’t exist by asking them why they don’t just suddenly float into space, all while telling them that floating is the highest form of locomotion according to your holy books.

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  • Pierce R. Butler

    “Grolar” (a word not found in the linked article) is a rather awkward neologism – but it’s way better than “pizzly”…

    If – as stated in the MSNBC piece – grizzy and polar bear ranges overlap, and mating seasons likewise, then why aren’t such “hairy hybrids” more common?

  • Greg Fish

    why aren’t such “hairy hybrids” more common?

    Well, we haven’t seen many of them since they’re a relatively new phenomenon, they live far out in the Arctic wilderness where very few people go, their numbers are still very small, and it’s thought that grizzlies only recently started venturing that far North thanks to climate change. All that will keep grolars from being a common sight in the Canadian tundra for quite a while.

    And yes, “grolar” is kind of a casual nickname which is why I chose a quick story that didn’t use this term in any official capacity. So far, the animal is more of an oddity to a zoologist than a fully fledged new species with its own classification.

  • Pierce R. Butler

    “Grizlar” for some reason strikes me as more impressive, but whatever name is finally chosen will probably be immediately co-opted for a line of SUVs or the like.

    … it’s thought that grizzlies only recently started venturing that far North thanks to climate change.

    An assertion explicitly denied in the linked article, which also implies that the two species’ ranges have abutted or overlapped for quite some time.

  • Greg Fish

    Ok, that was just a bad article and I changed it to a more reliable source which uses studies from the field for a much more accurate picture. I’m just going to chalk it up to the MSNBC’s writers not wanting to mention climate change lest they get deniers by the swarm, or their personal biases.

    In reality, there was no record of grizzlies venturing deep into polar bear territory prior to 1996 and the sightings have been slow, but steadily increasing. There is a slight overlap in their habitats, but in those overlaps, the bears tend to keep their distances away from each other and especially, each others’ food.

  • Pierce R. Butler

    A “bad article” – from MSNBC?!? But, but – “A fuller spectrum of news”! “something for every news consumer”! Chris Matthews!

    All right, all right, some of us would be better off leaving sarcasm to the pros.

    In fact, it seems worthwhile to defend the article, at least regarding climatology, with this quote:

    “If we want evidence for climate change, we don’t have to go to an isolated occurrence of a grizzly bear somewhere,” said England, who holds a northern research chair on environmental change in the Arctic.

    “The satellite imagery showing sea ice reduction over the last 30 years is proof positive of very dramatic changes in the northern hemisphere.”

    For all that, the piece did seem more concerned with whether the hunter whose trophy was the hybrid in question would get to keep his bear carcass than with the question of why licenses to kill polars (and now, apparently, grolars) are being issued at all.

  • boojy hall

    Hey wait, A polar bear and a grizzly bear are both Bears. They are not completely different species.

    And how can environmental stress allow or cause two different species to suddenly be able to breed? Or suddenly spawn a new species C.Or A can become B and B can spawn C. That is exactly what you said, “species are related”,” they may even spawn species C”. When can a cat and a horse or reptile and mammal breed?

    All dogs came from wolves, all dogs are dogs. All dogs can interbreed. No dog can breed with any other species of animal.

    I don’t understand how you can make statements like this

  • Greg Fish

    A polar bear and a grizzly bear are both Bears. They are not different species.

    Let’s see. They live in different habitats, subsist on different diets, generally avoid any interaction with each other and generally mate amongst themselves. Sorry, but that’s not the behavior of the one species, but that of two closely related ones. What you’ve done is the equivalent of looking at all the plants in your backyard, called them plants and said that they’re all basically the same when there are probably at least a dozen different species of them on your lawn.

    We could do the same thing with squid. All of them kind of look the same and swim with the help of a water jet, so they must be all the same, right? Never mind that they can range from the size of a pin, to the size of a small boat, or that they hang out in a range of different zones, in mostly separate groups, breed primarily with squid that swim where they swim, and eat what they eat. They must all be the same because a person who doesn’t understand taxonomies in zoology called them all squid, right?

    And how can environmental stress allow or cause two different species to suddenly be able to breed?

    Who said anything about that? I think you missed… well… just about everything said through the thread about grolars. Polar bears and grizzlies split into two species so recently that they can still hybridize. They’re now starting to mate on rare occasions because grizzlies can now venture much farther up North and still find food, and the occasional female polar bear that may be in heat, or induced to go into heat.

    When can a cat and a horse or reptile and mammal breed?

    If we go back enough it time, around the end of the Permian, mammals and reptiles could’ve hybridized since the predecessors to mammals, the synapsids, were quite close to their reptile ancestors. For cats and horses, you’d have go back roughly 60 million years, when they last shared a common ancestor.

    Your question shows that you a) have no idea how heredity works, b) have no grasp of even the most basic high school biology and c) that you didn’t read the post past a few paragraphs to which you could object. I explain that as lines of offspring resulting in different species keep accumulating new mutations over time, they can no longer hybridize with their ancestors because their genomes are now too different. Hybrids are just proof that an evolutionary split happened recently.

    All dogs came from wolves, all dogs are dogs. All dogs can interbreed. No dog can breed with any other species of animal.

    Dogs and wolves were split by humans only 10,000 years ago or so. The two could, and do easily interbreed. Know who else can interbreed? Lions and tigers. Horses and donkeys. And the list goes on. In other words, you’re wrong. I suggest you don’t quote creationist cranks who don’t know what they’re talking about.