The real story of human evolution

POSTED BY: SignyM
UPDATED: Saturday, March 25, 2006 22:05
VIEWED: 3424
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SIGNYM

Sunday, March 19, 2006 5:52 PM

Chromosomal studies of humans and the next most similar primates (gorillas, chimps, and bonobos) overlap +95%. Physical similarities, chromosomal overlap, and suggestive fossils all point to a common ancestor.

But there are many holes in the story of human evolution. No fossils show the transition from quadraped to biped. The process of HOW humans transitioned from hairy, tree-dwelling vegetarians to hairless, savannah-dwelling bipedal scavengers/ gatherer/ hunter ("Man the Hunter") hasn't been satisfactorily explained in common literature.

A few decades ago- probably before many people on this site were old enough to read- an explanation was popularized by such writers as Dr. Lionel Tiger http://anthro.rutgers.edu/faculty/tiger/ and Desmond Morris (The Naked Ape) http://www.desmond-morris.com. Their story focused on hunting as the driving force behind every unusual human feature. Why are we bipedal? Because bipedalism frees up our hand for hunting. Why did language evolve? To plan the next hunt and brag about the last one. Why are we hairless? To make sex sexier, so that females can continue to attract the male that brings home the food.

They point to baboons (who BTW are not close to humans) as a possible transitional stratgey: fierce troop defense and strong alpha-male organization, "combined with" a gradual emergence of human features. But most human features have significant disadvantages attached to them: bipdalism is not the fastest form of locomotion. Complex language (and the big brain that supports it) means an extended helpless infancy. And in an area that switched between sun and drought and torrential rains, hairlessness means exposure. After all, if human features were so advantageous, baboons would have drifted into that path long ago.

Some of you know where I'm going. The problems were resolved by proposing an entirely new pathway. First published by Alistair Hardy www.oundlesociety.org/SirAlistairHardy.asp this hypothesis assumes that humans are descended from primates that evolved at the water's edge and then returned to land.

Many human features are common among aquatic mammals: hairlessness, that nice layer of subcutaneous fat (that we all try so hard to get rid of!), linear orientation, the ability to manipulate small items by hand (otters for example), and the presence of a diving reflex. I became convinced that this was the most probable route to humans as we know them today. (BTW- both pigs and elephants also shared the same evolutionary history, having evolved in swampy/ watery areas and subsequently returning to land. They rank among the few hairless terrestial mammals.)

Additional evidence has accumulated over the years. The Afar Triangle and the Olduvai Gorge, where the most ancient proto-human fossils are found, is now a dry depression- but at the time the fossils were laid down is was a lake, or possibly a long bay connected to the ocean.

But perhaps the most interesting evidence is in the realm of human nutrition. People's nutritional needs reflect their evolutionary heritage. According to WHO, the most common deficiencies in inland humans are iodine, vitamin D and vitamin A- all readily obtained from fish. Another common- but unrecognized deficiency- in humans is the omega-3 oils DHA and EPA. also found in fish. In fact, this need for omega-3 oils for proper human brain development and function have led many biologist to consider- on that basis alone- a semi-aquatic evolutionary history. Here is one reference that I found in PubMed

Quote:
Evidence for the unique function of docosahexaenoic acid during the evolution of the modern hominid brain.

Crawford MA, Bloom M, Broadhurst CL, Schmidt WF, Cunnane SC, Galli C, Gehbremeskel K, Linseisen F, Lloyd-Smith J, Parkington J.

Institute of Brain Chemistry, London, United Kingdom. michael@macrawf.demon.co.uk

The African savanna ecosystem of the large mammals and primates was associated with a dramatic decline in relative brain capacity associated with little docosahexaenoic acid (DHA), which

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RUE

Sunday, March 19, 2006 7:03 PM

SignyM was kind enough to be very brief and encapsulate just a few of the many arguments around. There are many, many other seperate observations.

To address a more recent one, it was proposed that humans went from brachiating tree-dwellers directly to semi-aquatic fresh water dwellers. The existance of crab-eating Macaques (Macaca fascicularis) was cited to make that argument. However, there are reasons to believe the human story is based on salt-water adaptation, and specifically island dwelling.

One that I've been interested in is the relative need for and adaptation to different mineral profiles between humans and chimpanzees. (Salt-water and fresh-water mineral profiles differ significantly.)

The most dramatic is the tolerance for salt, specifically the salt sodium chloride. (Technically may different ionic compounds in combination are callled 'salts', NaCl is just one of many.)

Some of you may have read about the recent 'dramatic' breakthrough in treating cystic fibrosis. It's NOT a patented drug - in fact, there is no patent on it at all. It is cheap, it is easy, it is extrememly effective AND it is widely available. It is (TA DAH) inhaling a salt-solution aerosol. Why that is significant is that the whole genetic mechanism for chloride transport is HIGHLY conserved across the animal kingdom. The biggest obstacle to cystic fibrosis research has been the lack of available animal subjects, trying to find any animal with any mutation in the cystic fibrosis gene. Humans OTOH have over 2,000 separate mutations at last count. If humans evolved with salt-laden air, mutations in the gene would have been survivable, leading to accumulated genetic variation.

When it comes to diet, experimentally, one 'could' experiment with people to see if humans have a dietary salt tolerance. One piece of evidence that indicates they don't is the link between high salt intake and hypertention. However, high salt intake is usually linked to highly processed and/or preserved foods, and a lack of potassium in the diet (from fresh whole foods). Several articles I've read link hypertention to low relative potassium intake. Over a population, the lower the potassium intake, the higher the blood pressure. Additionally, the treatment for hypertension has shifted from salt reduction alone to DASH (Dietary Approaches to Stop Hypertention) which empahsizes fresh fruits and vegetables (high in potassium, and from green vegetables, magnesium), and is low saturated fat. In other clinical studies, low blood potassium linked to hypertention was treated in-hospital with potassium infusions. Roughly 10% of patients were refractory, and needed additional magnesium in order to treat low blood potassium. (Magnesium helps regulate blood potassium to maintian acceptable levels.) In my own family, when people have sarted to have their blood pressure creep up, eating or supplementing with additional potassium have been an effective non-drug method to bring it back down.

The information looks to me that it is trending to a high dietary sodium tolerance in the presence of adequate relative potassium and magnesium intake.

Humans also lack a 'salt appetite' which regulates how much salt one consumes. That is suggestive to me that that salt satiation signal was turned off in a high salt environment, since food (seaweed, crustaceans, shellfish, fish) came with a high salt burden that had to be tolerated.

Humans also have a relatively high iodine requirement. I think this speaks for itself. You simply don't find goiter in chimpanzees but you do in humans, as well as iodine-deficient cretinism and retardation, in areas where humans and chimpnazees co-exist.

Quote:
Iodine deficiency is, by a large margin, the most common preventable cause of mental retardation in the world. Endemic iodine deficiency remains a substantial public health problem in many parts of the world, including many areas in Europe, Asia, Africa and South America.

http://www.vivo.colostate.edu/hbooks/pathphys /endocrine/ thyroid/thyroid_preg.html

HAZE

Sunday, March 19, 2006 7:27 PM

Speaking from a personal perceptive when looking at the human being I see a creature evolved to walk. We may not be fast runners but we do have massive endurance. We can just walk and walk over very long distances. You have to question why such a treat would evolve in a creature that dowelled in coast areas or on an Island. We seem to me to be a creature perfectly suited to the vast flat plains of Africa.

Just my opinion of coarse.

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Who do you suppose is in there?

SIGNYM

Sunday, March 19, 2006 7:44 PM

Yes, walking bipedally is very efficient. Humans can outwalk a horse. But it may not be much of a survival strategy by itself. Plus, while walking may explain bipedalism, it doesn't explain the other unique human features and dietary requirements.

Rue- you an I share the same geeky hobby! When our daughter was born w/ a massive brain bleed in 1988, I consulted with the Los Angeles Regional Center to get the best advice. Among other things, breast feeding versus formula came up. The nurse told me in almost a conspiratorial whisper (looking carefully up and down the hallway first) that human breast milk has "something" in it that promotes brain growth. She spelled it out for me, I wrote it down: docosahexanoic acid. That was new research back then, near voodoo-magic. Now, it's widely recognized as a human requirement and sold as "molecularly distilled fish oil"! We've come a long way.

So, nutritionally, what do YOU think the "ideal" human diet would be?

PS_ I know there's a lot of research that shows DHA and EPA stabilize mood. I sometimes wonder if inland cultures - you know, desert-dwellers, jungle-dwellers and Senator Brownback (from Kansas) would be more reasonable if they ate more fish. :wry smile:

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Free as in freedom, not beer.

RUE

Sunday, March 19, 2006 7:57 PM

Haze,
I suspect that bipedalism allowed humans to return to savannahs (vs return to the trees), but the switch to bipedalism would have been hazardous. Humans just don't book on two legs.

And as SignyM mentioned, there are other physical, physiological, and biochemical features to account for:
evenly distributed subcutaneous fat (some account for that as a by-product of the need to lay down a large amounts fat for neurological development),
hairlessness (still a stumper; many many theories abound the most recent is to show a lack of parasites),
breath-holding (tongues not tied to the floor of the mouth, able to be moved back to close off upper respiratory passages),
and others.

It is possible that human proportion changed to allow full-time bepedalism, but that locking knees came later.

Nearly everything I know I learned by the grace of others.

CHRISISALL

Sunday, March 19, 2006 8:02 PM

Here we are, as usual, with Signy and Rue allowing facts and evidence to cloud their belief system...

I believe in evolution as told by the Flying Spaghetti Monster Chrisisall

RUE

Sunday, March 19, 2006 8:27 PM

SignyM,

I'm glad you asked !

One thing I didn't metion earlier was that humans have a high copper requirement relative to zinc (an oceanic ratio, not a terrestrial one). The best sources of copper (ratioed to zinc) are fish, shellfish, fruits and nuts, and possibly seaweed and other salt-water algae.

So, assuming as sea-side evolution:

low carb - seaweed is high in vitamins and minerals and soluble fiber, but low in carbohydrates
fresh - for K and Mg to offset Na
good source of iodine and copper
good source of DHA (and EPA)
sunshine (as skin type allows) for D, the 'sunshine' vitamin
constantly eating small amounts of food (not gorging then starving like lions)
chronic low-level activity

It's too bad that oceans are so polluted that everything comes contaminated with PCBs, dioxins, methylmercury, PDBEs and other seriously nasty chemicals. (In fact orcas that beach themselves and die have to be disposed of as toxic waste due to the high concentrations of these chemicals.)

Eat fish and shellfish known to be lower in contaminants. For example, farmed salmon is highly contaminated, wild salmon not as much. But a lot of fresh farmed salmon is sold as wild. So since only wild salmon can be canned (farmed salmon turns to mush) canned salmon is a better salmon bet.

Include fresh fruit and vegetables, and/or supplement with potassium and magnesium. Eat nuts which are a good source of copper, magnesium and healthful fats. Eat seaweed (good stuff! at least, I like it).

Buy organic grass-fed meat and poultry. Microorganisms in the dirt produce B12, some DHA etc, which are then concentrated in meat and milk.

Get lots of soluble fiber. (Seaweed is a natural source.)

Eat small meals often.

Avoid grains.

Don't worry about salt.

With apologies for clouded thinking.

SIGNYM

Sunday, March 19, 2006 8:42 PM

Quote:
I believe in evolution as told by the Flying Spaghetti Monster Chrisisall

Hey, that's funny, 'cause I believe in spaghetti too! Especially with Parmesan cheese!

But then, I read Rue's post on nutrition and now I'm not only gusatorially but also theologically conflicted!

Rue: I'm a big believer in whole food. There is a list of supplements as long as my arm (well, okay, maybe not THAT long, but still pretty long) that looked good in their native state only to prove harmful- or at least ineffective- when isolated: beta-carotene, genistein, vitamin E, lutien etc.

So seeing as my family barely tolerates fish (Kid is okay with shrimp and SO is okay with orange roughy, cod, and haddock- and never the twain shall meet on salmon!) is fish oil and krill oil a reasonable substitute? I DO try to serve fish once a week, but seaweed- ugh!

Also- and off-topic from evolution- do you think cinnamon and turmeric are all they're cracked up to be? And where is the evolutionary advantage to alcohol?

Okay, strike that last question- I don't care. I'll drink it anwyay!

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I'll go for free beer too.

RUE

Sunday, March 19, 2006 8:59 PM

SignyM,

There is some indication that additional benefits accrue from fish rather than just oil. However, most studies deal with fish oil, as it's easier to quantify the dose. So fish oil specifically is validated by research. I would go with krill oil if it's not too big a ding in the budget.

Cinnamon and turmeric -

I'm more familiar with the benefits of cinnamon as researchers have been more focused on isolating and testing its specific components. For example, cinnamon oil (fat soluble component) kills mouth germs associated with gingivitis which is associated with premature birth, low birth weight and heart disease. It also keeps E coli from anchoring to the bladder wall, and seems to slow growth of 'killer' E coli O157:H7. A water soluble cinnamon compound acts like insulin, helps existing insulin and normalizes blood-fat profiles. It also lowers blood pressure, thought to be due to its anti-oxidant activity which enhances NO (nitric oxide) persistance which relaxes blood vessels.

(As an aside, it kills mosquito larvae in ppm concentrations, making it an extraordinarily non-toxic pesticide.)

I've read some on turmeric, but not enough to get a feel for the direction of the research and results.

As for alcohol, now that's a topic for discussion in a pub somewhere.

HAZE

Sunday, March 19, 2006 9:21 PM

There is also the problem of why would a coastal animal that relies on the catching of sea life for nourishment need such vast brain power? In particular our capacity for entering the mind of our prey and anticipating its actions. This is a trait unique to humans amongst all other predators.

There is form of hunting still practised in Africa where by a lone hunter will peruse a prey item, this prey item is faster than the hunter is but the hunter has more endurance. The enters the prey items mind, anticipates it actions and movements and chases it relentlessly for hours and hours, until finally the prey dies of exhaustion. In this I see the original form of human hunting , and the reason for our big brain and our two legs.

Another question is why would a coastal animal need to be so adept and throwing things? We are incredibly accurate at throwing objects. Ever thrown a piece of paper into the bin from across the room? I’m firmly of the belief we evolved opposable thumbs so that we could better manipulate the stones we true to detour predators and startle or attack prey.

In short I’m still convinced we evolved in African flat land and moved to the coasts later.

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Who do you suppose is in there?

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