Did Humans Kill Off the Megafauna?

[Zar 696]

There is a huge debate in archaeology and prehistoric ecology wither or not humans killed off the Pleistocene Megafauna or if it was due to climatic changes? What are your thoughts on the question and what do you think happened to the Megafauna in the Americas?

 

Now you don't have to take a stand you can say both or one or the other. If you have some interesting thoughts on both sides please post!

[Speedskater 167]

I think blaming one simple thing into the extinction of mega-fauna isn't a valid argument. I believe almost everything is a conglomerate with large amounts of cause and effect.

[ViperSRT3g 224]

What might be interesting to see, is a comparison of the spread of humanity across the time span of the extinction of these species of animals. Then compare when and where extinctions took place and human influence.

[Speedskater 167]

Zar what's you're opinion on this? since you seem most interested.

[Zar 696]

Zar what's you're opinion on this? since you seem most interested.

Well, the concept of "environment" in contemporary ecology is "everything external to the organism". This includes climate, topography, and importantly, the behavior of other organisms plant and animal. In fact, it includes the social environment of conspecifics. The selection for one or another adaptive strategy from a suite of alternatives is often shaped not just by the behavior of the organism displaying the behavior, but by the frequency of the behavioral patterns of other organisms.

 

If a herbivore species of megafauna's range size is becoming fragmented by climate change, the behavior of predators is altered. If predation on the herbivore population is only from solitary carnivores (short faced bears or megalions) the demographic impact of that predation may largely target old, young, and sick. This predation might be different than predation from a social carnivore (dire wolves) where the demographic targets can be different. If humans are added to this system, the demographics will again change in composition because humans often target prime age females (beause of hides for instance). Notice the myriad combinations of "impacts" from this interdependence of cause with small alterations potentially cascading into sizable consequences?

 

However, I am in big favor of the overkill hypothesis and here are some of my thoughts. There are a handful of kill sites with mammoth and mastodon. All of which have spear points and processing marks in and on them. Kill sites are extremely rare especially for 10-13 thousand year old kill sites in any part of the world. So we know for certain that the Paleo-Indians hunted these type of megafauna. There have not been any kill sites for the other many types of megafauna (that I know of) however, that does not mean the first humans in the Americas didn't hunt them. Also we see a lot of the small mammals going into extinction as well. Even though we don't have kill sites for those either, doesn't mean that the paleo-indians did not hunt the other mega fauna.

 

If the rate of population growth for various intrinsic rates of natural increase are correct as shown in an article by Charles E. Kay then after 1000 years the population would be so large that these hunter gathers could easily hunt most of the animals into extinction just to support the population. And not just the large mammals but the small ones as well would become part of their diet.

 

Another good point is that it would only take 500,000 people to hunt the mega fauna into extinction. And so you can see that if the population of Paleo-Indians were over one million during these times how quickly the mega fauna could go extinct by not over hunting, but just by meeting the dietary needs of the population.

 

Now we also see a global climate change happening at the same time. This I agree also had an affect on the mega fauna by limiting resources and other factors on the diet of these large mamamls as well as forced accelerated predation. But it doesn't mean that it is the only cause for their extinction. Humans have to adapt to the climate changing just as much as the rest of the animal kingdom. And if these climate changes are making humans compete with other predators for food then humans will react and change their hunting behaviors as well. So both factors could come into play for the extinction of the mega fauna.

[ViperSRT3g 224]

If climate change were happening at the time of the extinction, then it could have been a contributing factor in changing the location of the animal's habitat. It could have forced them into a region more easily accessible by humans.