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Why human physiology is different from animal physiology

Posted: Tue Nov 08, 2011 2:40 pm
by hoosegow
This topic piqued my interest so I'm just throwing this out there for discussion. Basically it is why are we humans so pathetically weak compared to our animal counterparts? In this link http://www.slate.com/articles/health_an ... ingle.html
they state:

So the figures quoted by primate experts are a little exaggerated. But it is a fact that chimpanzees and other apes are stronger than humans. How did we get to be the weaklings of the primate order? Our overall body architecture makes a difference: Even though chimpanzees weigh less than humans, more of their mass is concentrated in their powerful arms. But a more important factor seems to be the structure of the muscles themselves. A chimpanzee's skeletal muscle has longer fibers than the human equivalent and can generate twice the work output over a wider range of motion. In the past few years, geneticists have identified the loci for some of these anatomical differences. One gene, for example, called MYH16, contributes to the development of large jaw muscles in other apes. In humans, MYH16 has been deactivated. (Puny jaws have marked our lineage for as least 2 million years.) Many people have also lost another muscle-related gene called ACTN3. People with two working versions of this gene are overrepresented among elite sprinters while those with the nonworking version are overrepresented among endurance runners. Chimpanzees and all other nonhuman primates have only the working version; in other words, they're on the powerful, "sprinter" end of the spectrum.

This got me to thinking about the "persistence hunting" concept and the endurance running hypothesis. This is where we basically slowly ran down our prey to the point where it is exhausted and we simply walk up and kill it (it is still practiced today). Coupled with the article I linked above, perhaps we are relatively weak in order to give us an endurance benefit to be able to run down our prey over long distance.

Re: Why human physiology is different from animal physiology

Posted: Wed Nov 09, 2011 6:05 am
by Ironman
Well, humans are animals...... :grin:
I think you pretty much answered your own question. We simply had different survival traits other than strength. You mentioned endurance, that is definitely a big one. Intelligence is another way, we are considerably better than other animals at thinking, and using this to our advantage. Surviving as a group is another strategy. So while strength worked, other advantages worked too. You lose things that you don't need too. Because the more attributes you have, like strength, intelligence, endurance, etc, the more food you need. So you get more of what is working, and lose stuff, when that loss doesn't impact survival value.

Re: Why human physiology is different from animal physiology

Posted: Wed Nov 09, 2011 10:42 am
by Paperclip
Well, our little brother is the biggest of all hominids. That's all what matters Image

Re: Why human physiology is different from animal physiology

Posted: Sun Dec 25, 2011 11:19 am
by Stefan 93
It is really inaccurate. For example, about those jaws... Monkeys have one muscle that is connected to the jaws which we don't have, but we have better jaws because something is in better angle or something, so we are better in that, I think kg for kg.
There are many reasons why we are weak. They do thousands of pull-ups every single day for their whole life and with only one arm! That must make their muscles bigger. Imagine if we could have done that from when we were 3-4 years old, we would be monkeys now.
And now every human can now survive, no metter how good he's genes are. And after 6000 years you can imagine what happened with genes...

Re: Why human physiology is different from animal physiology

Posted: Mon Dec 26, 2011 11:43 am
by Matt Z
I don't really beleve that. Apes are able to cling to their mothers from birth. No human infant can do that. Likewise, gorillas in zoos don't get much exercise, but they're still extremely strong.

It's possible human ancestors gave up some strength for increased endurance ... Not neccessarily for running down healthy prey animals, but rather for walking long distances in search of food, or perhaps for tracking undisturbed or wounded prey.

Re: Why human physiology is different from animal physiology

Posted: Mon Dec 26, 2011 11:45 am
by Matt Z
Also, it's possible modern apes are stronger and faster than the prehistoric apes from which hominids evolved. After all, we're not the only ones that are still evolving.

Re: Why human physiology is different from animal physiology

Posted: Mon Dec 26, 2011 8:41 pm
by Ironman
I think your first answer is the best. Our common ancestor with the gorilla for example, should be very similar to the modern gorilla.

Re: Why human physiology is different from animal physiology

Posted: Mon Dec 26, 2011 9:33 pm
by stuward
Ironman wrote:I think your first answer is the best. Our common ancestor with the gorilla for example, should be very similar to the modern gorilla.
I don't think that's true. Like Matt said, the gorilla would have as long to evolve as we have. The environment that we shared was likely the edge of the jungle. Humans took to the plains while the gorilla took to the jungle and would have adapted to that new environment. We split from orangutans before gorillas yet we share several unique physical traits with them. The speculation is that they continued to evolve along parallel lines with humans, sort of like some Australian animals being similar but unrelated to other animals.

The best candidate for a common ancestor is Nakalipithecus, and all that exists is a jawbone and some teeth.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 2:14 am
by robt-aus
Christopher McDougall's recent book "Born to Run" expands on the theory and practice of 'running down'. I recently borrowed this book from work. His story of an awesome endurance event delves into entertaining coverage of the science and motivations behind ultrarunners. In it he interviews researchers who put forward that neanderthals when compared with homo erectus exhibited significantly higher strength and heavier more muscular bodies and would take far more aggressive, confrontational team based approaches to killing animals. I believe (from memory) he then quotes a researcher who coined the phrase "a neanderthal was like a cross between an olympic athlete and a rodeo clown". The subsequent extinction of the 'thals is then touched on, with a few gaps in the process and some cheeky comments on the superior endurance and tactics used by homo erectus.

Rationally it makes sense from power to weight ratio and the energy requirements of mass. Practically, lower injury and fatality rates from not directly attacking the big nasty animal might be just as important.

McDougall also mentions the breakfast salad, carb loading in the style of a traditional Mexican hill people and the regular consumption of low alcohol corn based beer. I try to support each of these from time to time.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 11:40 am
by Jebus
robt-aus wrote:The subsequent extinction of the 'thals is then touched on, with a few gaps in the process and some cheeky comments on the superior endurance and tactics used by homo erectus.

Rationally it makes sense from power to weight ratio and the energy requirements of mass. Practically, lower injury and fatality rates from not directly attacking the big nasty animal might be just as important.
Homo sapiens share genetic links to the denisovans, neanderthals and homo erectus. Only certain populations in sub-sarah africa don't share any of these links, apart from erectus obviously. So we modern humans are not confined to marathon type running, though we are very good at it.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 3:00 pm
by Matt Z
"The subsequent extinction of the 'thals is then touched on, with a few gaps in the process and some cheeky comments on the superior endurance and tactics used by homo erectus." - robt-aus

I think you might be confusing Homo erectus with Cro-Magnon Man (early modern humans). I'm pretty sure the Neanderthals evolved from Homo erectus and persisted as a distinct species/sub-species after Homo erectus went extinct.

"So we modern humans are not confined to marathon type running, though we are very good at it." - Jebus

Compared to apes, modern humans are pretty good distance runners. However, compared to most ungulates we just plain suck. ... I have a really hard time accepting the idea of early humans running down big game, partly because there are so many easier ways to hunt. There's also evidence of early modern humans using other hunting methods.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 3:06 pm
by robt-aus
Matt Z wrote:"The subsequent extinction of the 'thals is then touched on, with a few gaps in the process and some cheeky comments on the superior endurance and tactics used by homo erectus." - robt-aus

I think you might be confusing Homo erectus with Cro-Magnon Man (early modern humans). I'm pretty sure the Neanderthals evolved from Homo erectus and persisted as a distinct species/sub-species after Homo erectus went extinct.
I think you are right. Looking at the march of progress indicates the time periods between species are too large and the quote doesn't really make sense. I'll see if I can have a look through the book today and be a bit more precise about what was being said.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 4:03 pm
by hoosegow
Matt Z wrote: Compared to apes, modern humans are pretty good distance runners. However, compared to most ungulates we just plain suck. ... I have a really hard time accepting the idea of early humans running down big game, partly because there are so many easier ways to hunt. There's also evidence of early modern humans using other hunting methods.

You and I being of larger stature and cringe at running 100 yards much less 20 miles. However, there is a lot of evidence that persistance hunting was practiced by just about all the ancient humans. There are so many easier ways to hunt, but when did those ways become known or developed? What did we do before that?

Now I agree with you that many ungulates have some pretty good endurance. The wildebeast comes to mind, but not all do. If you think about the world record in the marathon is just a few minutes past 2 hours. Let's be conservative and say that a good athlete can run one at 10 mph which would put them over 2.5 hours to complete. How many animals can run 10 mph for 2.5 hours straight?

I think to catagorically dismiss the possibility that our endurance was key to our development is not wise. Couple this with we are relatively weak and compare how muscle fibres contribute to that and I think you can draw some intersting possible conclusions.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 9:44 pm
by Matt Z
Bison can run for days!

Meanwhile, how far could a man chase a deer or antelope before losing sight of the animal? After that he'd have to resort to tracking. How fast can a person actually move while tracking game?

There's evidence of stone age man stalking and ambushing prey, driving entire herds over cliffs, setting traps and snares, etc.

I don't see why a group of hunters in a game-rich environment would bother chasing one uninjured animal for 20 miles. That type of hunting only makes sense if game is scarce and the selected target is somehow weakened (sick, injured, very young or old).

I think endurance WAS important, but it probably took the form of long-distance walking more often than marathon running. Rather than chasing one animal, hunters would have followed migrating herds.

Re: Why human physiology is different from animal physiology

Posted: Tue Dec 27, 2011 9:54 pm
by robt-aus
The book's currently on loan to someone else. However a quick skim of the reviews of this title on a well known website indicates reviewers using the terms homo erectus, homo sapiens and 'our cousins' when discussing the comparison made with neanderthals (chapter 28).

Two of these species do not appear to have existed at the same time based on the timelines in the wikipedia timeline on the march of progress.

Evolutionary biology isn't my thing, and given the nonlinear nature of evolutionary change I'm not going to dig too deeply into the faults in the march of progress. Considering this factual shadow over the idea of endurance as a strategy and tactic as presented in this book, which is the only place I've read about it, I can still see an evolutionary reason for dropping weight/mass to enable endurance based activities. But I would say that, if you've read my log :)

The other human (homo sapiens) attribute mentioned as important was (is) our ability to respirate independently of skeletal movement and to perspire efficiently. There are several unscientific examples given of people who have successfully outrun horses over suitable, quite long, distances.

Have just read Matt's reply: one thing we're not talking about is timeframes, and of course hunting tools/techniques were used in different circumstances at different points. One review I skimmed mentioned bows and arrows were only around 30000 years old. In terms of tracking, remember we have moderately good eyesight, but our pattern recognition skills have always been superior to most animcals. If you're a plains dweller, perhaps the best tool was a tracking an animal to exhaustion. We're good at developing specific tools for specific jobs, but it does take time and a hominid's gotta eat.