Ice Age Physiology

[Guest]

Urkel,

 

 

 

"And both Stahl and Gehr, et al. indicate that as mammalian mass increases, lung capacity increases, I've simply postulated that as superior oxygenation increases, then size increases.  This is a chicken and the egg argument."

 

Increase in O2 partial pressure may ALLOW larger size but would not necessarily increase size itself. Animals in hyperbaric systems do not grow larger. Growing larger requires adaptation to numerous conditions that are brought on by the increase in dimensions, mass (and hence weight), and the distribution of O2 and nutrients in the blood. Growth on an evolutionary scale is not a simple direct growth curve. The size of species undergoing evolutionary changes to large size is not to scale. Larger animals need even larger feet for instance with legs with wider cross-sections than their smaller kin to resist breakage. All of this is brought about via minute mutational adjustments that do not appear on cue.

[hiflier]

Hello JDL,

 

If CO2 levels were higher say 100,000 years ago- WHICH THEY WERE! Then a cycle of plant growth and abundance churning out more O2 might be the case. The discussion of greater O2 levels resulting in larger insect, bird amd mammal would then seem to have a jumping off point with higher O2 atmospheres. We're generating CO2 in addition to the natural Milankovitch cycles of warming/cooling so I would expect again, to see larger insects, birds and mammals in our future.

Edited February 14, 2014 by hiflier

[Guest]

hiflier, That doesn't follow. Plants in high CO2 conditions close their pores (which take on the CO2) when the leaves have enough. The higher level allows plants to maximize their photosynthesis and O2 output but only to a limit. When their limit is reached, the pores close up and the plant then goes to work. This does mean that plants are not as limited by water availability and heat though. Plants that can close their pores before they transpire out more H2O than they take in can grow more.

 

Larger insects and other animals will require evolutionary pressures and new genes to allow that. Simply putting dragonflies in a high O2 environment will not make them grow bigger. Some of their descendants may grow bigger as higher O2 will allow that, but there will remain many smaller species of dragonflies just as there were during the carboniferous period.

[hiflier]

Hello antfoot,

 

I'd be remiss if I didn't welcome you to the Forum as a first step. So, welcome.  You have a good sense of things it would seem and that is a valuable asset whenever an effort to bring science into the mix helps the picture. And oh, I agree that changes will not be immediate and yes, size ranges will be present. I have no issues at all there Living organisms in the past WERE larger and the thread is trying to zero in on the concept of that. It's complicated as you are more than likely aware even to the point of surmising if colder oceans supply wider areas with the same concentration of nutrient rich water as say, the Antarctic Ocean. Bigger fish?

 

Yeah, it's complicated but I hope were not reinventing the wheel here. I'm sure there are at least arvix papers on this sort of thing. Again, welcome.

 

Wow, just saw your post count, then welcome back I should say

Edited February 14, 2014 by hiflier

[Guest]

Thanks Hiflier.

 

My main point though is that there is no relationship between the O2 level and the "giants" "found" in the Midwest. The OP suggested that increased O2 levels due to a drop in sea level made giants but that higher O2 level would have been below modern sea levels and not where we find the giant animals of the Pleistocene which is largely on the steppes and grasslands higher above. Even if the giants from the Midwest were real, they would not have been giants because of the O2 levels. Most of the mega-fauna of the Pleistocene (and most other eras) were large because of the large quantities of food they needed to eat. Most of the mega-fauna were grass eaters. Grass (and many other foliage types as well but grass especially) is a low nutrient food source. Herbivores that eat grass need especially large guts to digest it. Especially large guts need especially large muscles to carry them around. Hence the herbivores get huge. Carnivores that hunt mega-herbivores need to be bigger too or smarter. Wolves got around their prey by being smarter not bigger. An intelligent hunter like humans would do the same thing. Humans would not grow to be giants for hunting because we are smart and saving energy and nutrients for making more humans is evolutionarily more sensible.

[JDL]

Antfoot, there would be some increase in O2 partial pressure relative to today simply from the colder, denser atmosphere, even at non-coastal altitudes.

 

Any effects would, of course, be evolutionary.  It would be interesting, though, to read any studies on aerobic bacteria grown under hyperbaric conditions over extended times.

 

Bottom line, better oxygenation should lead to more efficient physiology and a better chance for organisms to reach their optimum potential for the contemporary conditions.

[Guest]

JDL ^

 

Such levels would decrease during interglacial periods. We see no reduction in size nor do we see sudden extinctions linked between giants and these O2 level reductions. Mammoths survived in numerous forms through at least three interglacial periods that I am aware of without noticeable size fluctuations. I really doubt the relatively small increase in O2 would have such a dramatic effect on life forms. You were postulating that these species became extinct at least in part due to the reduction of O2, if I remember the OP correctly. The most reasonable cause of the recent mass extinction of mega-fauna is most likely the arrival of humans. Most of the large birds, reptiles and mammals that died out did so after humans arrived in their lands. Modern elephants are larger than most of the mega-fauna that went extinct at the end of the last ice age.They do not need higher O2 levels to be as big as they are.

[JDL]

So presumably, a megafauna species once evolved, could well persist beyond the conditions that gave it rise, unless subjected to other pressures, such as being hunted to extinction, or loss of its specialized food sources.  This makes sense to me, the refined hypothesis still hinges on ice age conditions fostering megafauna development, but provides that megafauna can survive interglacial periods, unless brought to extinction by other means, such as the event leading to the Younger Dryas Great Freeze, which is believed to have occurred over the course of as little as a decade, to have markedly reduced vegetation in the northern hemisphere, and to have resulted in the extinction of most megafauna.

 

Bigfoot, like man; intelligent, adaptable, and opportunistic, would have been more likely to survive such an event by means of migration and the ability to survive on multiple alternative food sources.

[Guest]

^  "the refined hypothesis still hinges on ice age conditions fostering megafauna development"

 

The ice age was not just colder but drier. This fostered the spread of grass and grass feeding herbivores. That so many of these herbivores were huge is due to their needs for larger intestines and stomachs to process their food. That necessitated larger bodies to carry them. There are many grass feeders that do not get large (largely cud-chewing artiodactyls. Chewing the cud reuses the teeth and jaws to process foliage unlike non-artiodactyl species which need larger guts to do the job)) but most of the species that did get large were grass eaters. Those herbivores that fed on trees had to walk farther to find them in these colder and drier habitats. This also necessitated larger size (think ground sloths and giraffes and elephants as well).

[norseman]

I'm confused.

 

How would humans have not capitalized on the same conditions in the last ice age as Squatch?

[JDL]

Antfoot, predators also reached megafauna proportions.

 

Norseman, with respect to hominids, squatch certainly appear to have done so.  Both Homo Erectus and Homo Heidelbergensis also reached impressive statures.

 

With respect to humans, there appears to have been a race of larger people who are now extinct.  They were likely "human". 

 

Why were there also humans of normal size?  I'm not an expert, but I would speculate that a combination of latitude, societal development, and selection made the difference.  Larger races further North, smaller further South.  Smaller size would support larger populations in communal, non-nomadic societies with regular food sources.  And with the safety of numbers, there would be less pressure to select for robustness.  Selection for larger size would make more sense for smaller groups living semi-nomadically rotating from foraging/hunting ground to foraging/hunting ground.

[Guest]

^ Homo heidelbergensis was not especially tall compared with modern humans. None of the fossil remains I know of are especially tall at all. Robust is the word I read in many reports but that is not the same as giant. I've read stories about giant skeletons but no reports of studies on these skeletons. I presume that they are false reports. Fortean Times often has them. I do not consider FT to be a reputable scientific source however.

[JDL]

I don't go in for the Fortean stuff.

 

It appears that there are multiple representations in academia regarding Heidelbergensis height.  I'm seeing everything from 5'9" to 7', which does not surprise me.  My understanding is that erectus could push 6'6".

 

I have actually seen Si-teh-Cah skeletons on display in the Mark Twain Museum in Virginia City, Nevada.  The three I saw (more than once) were recovered from a cave near Walker Lake and were as large as represented.  The female well in excess of six feet and the male in excess of seven.

 

The Si-teh-Cah were called stick thrower Indians due to the fact that they were still using atlatls when the Paiutes had long since been using short bows.  For the shorter Paiutes, the short bow provided greater penetrating power at distance.  For the stick throwers, the atlatls were apparently the better weapon because of their longer arms.  Either that or they were just too backward to adopt the bow, which doesn't make sense.

 

Given that large remains did, in fact, exist in Nevada, verifying Paiute legend of an extinct race of giant indians, I am not prone to dismiss other accounts of such throughout the Americas.

[Guest]

Considering Mark Twain wrote about a petrified giant, tongue in cheek, I find it hard to see giant skeletons in a museum devoted to or named after him as anything other than a joke he might appreciate. Even without that however, 6 foot women and seven foot men aren't really that unusual. Most populations have a few of them. I don't dismiss such reports out of hand but do realize that humans are subject to exaggeration. The museum's site didn't mention the giant skeletons but I also didn't dig too deep. If you can find a more particular reference I'd love to read it.

[JDL]

They were on display in the 60's and 70's.  BLM has the remains now.  We discussed this in detail a couple of years ago on this forum.  There are multiple threads available for review.

 

I viewed them several times.  Based on the artifacts found with them and the relative size, they appear to be of the same tribe or race as the Lovelock cave find.

 

Keep in mind that the average Paiute of the day was a shade over five feet, making these people two feet taller than the contemporaneous Paiutes.