Grip Evolution

Here’s another story to add to the slew of news articles about general health trends:  human beings, on average, are getting weaker.  In this case, the indicator is grip strength — that is, how much holding and squeezing force can a person generate with just the fingers of their hand.  Recent studies have indicated that grip strength has declined significantly, even in the last 30 years.

So what, you might ask?  You’re less likely to encounter the guys who give you a bone-crushing handshake, and you don’t see people walking around flexing those hand exercisers anymore.  What’s the big deal?  The big deal is this:  grip strength is one of those inverse health indicators lurking in the human body, with lower grip strength associated with increased mortality from all causes and cardiovascular mortality in particular.  And, especially for those of us who are getting up there, grip strength is a key indicator of sarcopenia, the loss of muscle that occurs as we age, and may also indicate issues with cognitive performance.

Why is grip strength declining?  Of course, gripping is a key part of the evolution of homo sapiens — whose distant ancestors needed a strong grip when they were swinging through trees, and whose more recent predecessors used their hands to create and then wield tools and weapons that allowed them to survive predators and gather food.  In short, humans needed that strong grip to make it through the natural selection melee and emerge at the top of the evolutionary pyramid.  But in recent years, the need for hand strength at home or on the job has declined.  White collar workers need hand dexterity as they tap away at computers, not hand strength, and even blue collar workers now use automatic tools that don’t need the kind of personal strength that hand wrenches of the past, for example, required.  Mix those factors in with a general decline in fitness and increase in obesity, and you’ve gone a long way to explaining why human beings increasingly are becoming a bunch of unhealthy softies.

In short, as a species humans may be losing their grip.  It’s not a positive development.

Hairless And Sweaty

At some point in the past, humans and great apes had a common ancestor.  The homo sapiens branch of the tree then veered off in one direction and evolved into the humans of today — largely hairless, especially in comparison with other primates, except on the head and in the nether regions — whereas the great apes remained heavily furred.

What caused the humans to take the smooth-skinned route?  The BBC has an interesting article that attempts to answer that question.  It’s not an easy question, because having a mat of fur seems to have lots of evolutionary advantages.  It protects the skin, is warmer, provides some protection against bites, and may even have a camouflage effect.  So why did the most successful primate in the history of the planet, the one that reached the top of the food chain, ditch the fur at some point in the distant past in favor of the bald look?

The theory is that the evolutionary forces began to work when our early ancestors moved out of the shadowy forests and into the savannah.  By getting out of the shade, the proto-humans moved to a setting that offered more hunting targets, more meat, and thus more protein, which would help them to develop bigger brains.  But, the savannah also featured more heat.  The heavily hirsute creatures who tried the veldt quickly became overheated and had to retreat to the cool forest, where they were left to snack on grub, worms, insects and fruit.  Our less furry ancestors were better able to adapt to the heat, and those who had more sweat glands and could sweat away the body heat were even more capable of running after and killing protein-packed prey in the hot African sunshine.  The standard forces of evolution — time, survival, and procreation — then combined to shift human bodies increasingly away from shaggy fur and toward sweaty hairlessness.  The end product was the modern human, which is both hairless and also the sweatiest primate alive.

Sweaty and hairless.  It’s almost as if evolution was trying to design a creature that could survive August in the Midwest!  Now if evolution would only answer another crucial question:  why do men who reach the AARP membership age seem to lose all of the hair on their legs?

Species-Saving Sex

Don’t look now, but the history of homo sapiens — and of human-like creatures on planet Earth — is getting progressively weirder and more titillating.

Scientists conducting studies of human genes are learning lots of interesting information about the development of our species.  One of the more provocative findings is that our genetic information indicates that there were multiple instances of significant homo sapien interbreeding with other human-like species — specifically, the Neanderthals, and a mysterious, largely unknown species called the Denisovans —  that left indelible marks in the DNA of modern humans.  And it also appears that the cross-breeding provided us with some useful genetic material, including genes that enhanced the operation of the human immune system and helped our ancestors fight off pathogens.

Not much is known about human history before the dawn of civilization.  Most of what we understand comes from looking at fossils of human ancestors and attempting to piece together the gnarled branches of the human family tree.  Human genetic analysis provides a different kind of window to the past of our species.  It’s now obvious that the early days of the human species saw our ancestors competing with — and apparently having lots of sex with — other hominid species.  We couldn’t have been too much different from them, because the genome evidence means that when humans had sex with Neanderthals and those enigmatic Denisovans, their one-night stands produced pregnancies and non-sterile offspring that, in turn, shared their genes through mating.  All of that cross-breeding among different species helped to make humans what they are today.

We might never learn what happened to the Neanderthals, or the enigmatic Denisovans, and why they died out while humans survived and became the dominant species on the planet.  What we can now say with some confidence is that human ancestors apparently were as interested in sex as modern humans are, and weren’t particularly troubled about who — or what species — they were having sex with, either.

Smelling One Trillion Smells

A study recently estimated that human beings can detect 1 trillion different smells. At least half of those smells apparently are found somewhere in the average high school boys’ locker room. (Just kidding!)

In the study, the researchers mixed different “odorant” molecules in combinations, provided participants with three vials of scents, and asked them to identify the outlier in the group. The participants were, on average, adept at distinguishing between the different smells. The researchers then multiplied the different combinations to come up with their estimate of one trillion. Believe it or not, one of the researchers is convinced that the estimate of one trillion — 1,000,000,000,000 — is almost certainly too low.

One trillion is a lot of smells, but the conclusion is plausible from an evolutionary standpoint. The researchers believe the odor-detection capabilities are directly related to the hunter-gatherer history of homo sapiens, because our distant ancestors relied on their sense of smell as a key component in their ability to track prey, sense enemies, determine whether food remained edible and water was potable, and otherwise detect danger. If you couldn’t smell a silently approaching saber-tooth tiger and skedaddle, or make a judgment that the fly-blown piece of woolly mammoth haunch that you were planning on eating for lunch remained edible, you weren’t likely to survive to reproduce.

The recent study joins other studies that indicate that human senses are remarkably discriminating. Along with the ability to use our olfactory capabilities to detect one trillion smells, other studies conclude that the human eye can distinguish between several million shades of color, and the human ear can discern 340,000 different sounds. Talk about sensory overload!