I think it’s generally accepted that human beings have been growing taller over the past several centuries as diet and health have improved – any glance at very old doorways or at human artifacts in museums will attest to this. But have animals undergone the same process? Have human interferences in the animal kingdom either stunted their growth, or make them grow larger than ever before? How about domesticated animals? You often see commercials for dog food claiming to be chock full of ingredients to help your dog grow – a big improvement from the days when dogs were just given leftover scraps from the table. Are dogs today much bigger than they were a few centuries ago?
One complication to this question is that most domesticated animals are subject to a greater or lesser extent to artificial selection by man. So if there was a breed of dog, say, that humans wanted to make bigger they would be getting bigger. If there was a breed that people wanted to make smaller they would be getting smaller.
On possible example I can think of is birds like turkeys and chickens that are bred for meat. Domestic turkeys are definitely heavier than their wild cousins and this difference has probably mostly occured over the last 500 years or so. Some of this is probably due to genetics (again, artificially selected by humans), some to diet/lifestyle.
I can’t think of any reason why wild animals in general would be getting either bigger or smaller. The term “wild animals” covers a vast array of taxonomic groups spread out over the whole world so it is probably impossible to make such a generalization.
To give one specific example though I have heard that the coyotes that are found in the Eastern US tend to be larger than their relatives in the West. Also animals like racoons that live in the suburbs and eat garbage thrown away by humans tend to be heavier than their relatives that live far away from human influence, but this difference may be due solely to diet.
To clarify: coyotes were not originally native to the Eastern US and have only really moved into the region over the last 100 years or so. So it is possible that humans have somehow inadvertantly affected the local environment to somehow select for larger coyotes.
In some cases undomesticated animals might “select” for smaller size as human predators want the big ones. I have no cite for this, but recall reading that this may be happening in some types of fish. Those that are genetically small even as adults may be more likely to be thrown back.
This is correct. In some species of commercially exploited fish, the size at maturity has been going down because of overfishing of the larger size classes.
One example is shrinking salmon..
As I understand it, popular hunting animals like deer are getting smaller, because human hunters kill the biggest ones first.
On a related note, pressure from poachers is causing the rapid spread of elephants with small or no tusks. Link
Probably not. The larger size is most likely due to hybridization with red wolf populations.
The jury seems to be out on this. Part of the problem is several of the online sources I have looked at just say there is genetic evidence Eastern coyotes have hybridized with “wolves” without specifying what type.
This article suggests that the larger size of Northeastern coyotes may just be a manisfestation of a phenomenon that is seen in other species, that individuals found further North tend to be larger. I suppose there could also be a founder effect at work, if the Eastern population has descended from a relatively small number of individuals.
While I have never had the “pleasure” of seeing one, I know many people who have seen NYC rats. Apparently there are some really huge ones running around there. I’ve also seen some comparable reports in the media.
The WAG would be that a city such as NYC would have a lot of primo food for the rats, they have a short lifecycle, etc. So in a couple hundred years, rats the size of a beagle.
While it’s certain that humans have grown bigger it’s very doubtful if glancing at doorways or museum peices will tell you that.
Museum peices tend to be odd sized simply because common sizes of clothing, furniture etc were used until they broke. When someone was a dwarf and needed to have special furniture and clothing made they were the only people in the town who could use it. When they moved or died the item was either destroyed through recyclingor else placed in strorage. And only those items placed in storgae wound up in museums. That’s further complicated because diplay peices of furniture and clothing were usually miniatures. Nobody actually sat in 6" chairs or wore size 4 shoes but the manufacturers made such sizes for display purposes because they were cheap to make and easy to fit in a display window.
With doorways there were two very good reasons to make them small. The first was that heating was expensive and crucial to survivial. A large door let out a lot of air every time it was opened, giving a good incentive to doors that everyone had to duck to use. Much like an igloo door. The other factor was the avialability of wood. In the days before plywood most doors were restricted in size to the size of the planks. Large planks were more expensive than small ones, hence once agian we have small doors.
People certainly have grown in the the last few centuries, but you can’t tell that from these sorts of examples, and peoplehaven;t grown as much as they might indicate.
No doubt about that. There are numerous examples of animal species that have become dwarfed as a result of hunting, from all parts of the world.
That depends what you mean by ‘dogs’. Large dogs tend to be set in established breeds, and established breeds have standards. Any animal that falls oustide of a standard becomes worthles to a breder. As a result I have known a few breeders who have starved (not severely) dogs in their first year when they thought they might outgrow the breed standard. Because of that sort of thing, and the simple fact that outsize dogs aren’t bred from, it’s very doubtful if any dog breed has become any bigger in recent years.
As for other animals, it seems pretty obvious that cattle, pigs and chickens at least have become much, much larger than their ancestors. The larger breeds of those species today would easily be twice as large as their ancestors 400 years ago. Our modern livestock tend to be giants. But that is on large part because for a long time we dwarfed our livestock. Animals were housed with peoplel in much of Europe thorugh the winter months and large animals were selected against. However our domestic pigs, horses and sheep are stillarger than their wild ancestors, while the largest of domestic cattle are probably larger.
This is not quite true. A dog which is bigger (or smaller) than the breed standard can still be bred from, and some dog breeders are no more immune to the human love of novelty than the rest of us.
Dogs which don’t follow their standard exactly can still be registered and shown, and even if they never win championships they can still be bred. And in some breeds size is rewarded in the show ring by some judges.
Humans being what they are, there is something of a craze for dogs which are both much bigger and much smaller than, say, fifty years ago. Great Danes, as one example, have increased quite a lot in height, and changed in significant other ways from dogs which might have been shown at the turn of the century, as have other giant breed dogs.
This hasn’t got much to do with nutrition or natural selection, but rather with human fascination for very big or very small (i.e. teacup chiahuahuas), most often, sadly, to the detriment of both the breed overall and to the individual dog.
Chickens I’ll certainly agree with, and I’ll take your word on pigs. But are you saying that modern cows are larger than aurochs?
No, most modern cows are much smaller than the Aurochs. It is possible that it was preferable to select for an animal that was more easily controlled than one that offered more meat on the hoof.
Straight Dope Staff Report: What did cows evolve from?
As I understand it, there has been an increase in average height over the last several generations in the developed world but that’s mostly due to better widespread childhood nutrition, and it’s not as dramatic as is sometimes imagined, for all the reasons **Blake **points out. This is of course, not a genetic change.
For coyotes, I believe a big part of it is that humans did alter the environment, by removing wolves. That left a niche open for larger coyotes, who now had lots of offspring, as opposed to being killed by wolves, which would have previously happened. Result: coyotes are getting larger genetically.
Slight hijack:
I’ve also read that poachers have placed evolutionary pressure on African Elephant populations by killing so many elephants for their tusks that tusklessness is more prevalent in recent generations.
No, in fact I said exactly the opposite. “pigs, horses and sheep are still larger than their wild ancestors, while the largest of domestic cattle are probably larger.”
What I am saying is that the ancestor of a modern Santa Gertrudis or Sussex, breeds that average about a tonne at maturity, or a modern Chia that averages 1 1/3 tonnes, was a 16th century animal that weighed 500kg maximum. There’s no doubt that cattle have become much larger in the last few hundred years alone.
Now whether cattle are larger than aurochs is a matter of some debate, because of course nobody can even decide what the ancestosr of domestic cattle were, nor how many candidate species there were. The latest evidence is that domestic European cattle are descendents of North African cattle, and that these may or may not have been the same species as the European aurochs. Whatever the case the African wild ox was not the monstrous 6 foot animal desciribed in Colibri’s article as the ancestor of modern cattle. Instead it was a much more mundane beast witha height of about 160cm, 0r 5’3" at the shoulders. That’s pretty much identical to the modern large breds like Santas, though it would almost certainly have been nowhere near as heavy as those breeds. Compared to really heavy breds like modern Chias they are considerably smaller. That small size may well be why the African species/subspecies was domesticated, and why it appears no European aurochs ever were.
So as I said, it’s probable that modern cattle are larger than their wild ancestors, but until it can be established precisely what those ancestors were it’s all up in the air.