Why Opposable Thumbs Exist

Why do opposable thumbs exist in humans and other primates?  Scientists generally agree that the appearance of the opposable thumb was a key evolutionary point in the development of our species.  It is what allowed primates to grip and climb and move into the trees, away from the realm of large predators looking for a meal.  Opposable thumbs also proved to be pretty handy from a toolmaking and tool using perspective, whether the tool was a stick to be manipulated or a rudimentary axe.

All of this is true,  Curiously, however, scientists haven’t fully explored whether the opposable thumb was developed in anticipation that modern humans who are too cheap to buy a nozzle for their garden hose might need the thumb to water their yard and plants on a beastly hot summer day.  Sure, the opposable thumb might not have been evolved specifically for watering and hose wielding, but it sure works well for that purpose — whether you want to generate a gentle sprinkle or a high velocity jet to reach the side of the yard beyond the length of the hose.

How do we know for sure that our distant ancestors weren’t big on watering?

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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.

best-hand-gripper-exercisesSo 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.

Sleepless, But On Guard

Everyone knows that, as you get older, your sleep patterns change and, for the most part, get worse.  A lot worse.

The arc of sleep goes from the totally out like a light sleep of the very young to the 12-hour power-sleeping capabilities of college students, but it’s all downhill from there.  By the time you’re in your 40s, 50s, and 60s, the realities of shrinking bladder capacity and ever-present concerns about developments in your career and family life combine to make sleep a fitful exercise, with lots of tossing and turning mixed in.  There’s not much REM sleep to be had.

neanderthalerScientists think there is an evolutionary reason for this unfortunate trend — one that goes back to caveman days.  They say older folks sleep less soundly because their role in the tribe was to be alert for potential predators, attacks from warring clans, and other lurking disasters.  In caveman days, the blue-haired set would go to bed earlier than the rest of the tribe.  Then, with their lighter sleep habits, they would be roused by the sounds that a nocturnal animal would make upon entering the cave and could give the alert, so that the more youthful members of the tribe could help to fight the predator.  And the sleepless oldsters would also be first up in the morning, to get that all-important fire going and be ready to deal with any unwanted intrusions by bears or wolves or sabertoothed tigers.

It’s nice to know that there’s an exciting explanation for experiencing poorer, less satisfying sleep as you get older, and that in the dawn of humanity a codger my age would be quickly roused to alertness in order to grapple with cave bears and save the tribe.  I’d still trade it for a solid seven hours of sound sleep.

Our Tangled Family Tree

Consider Homo naledi.  A humanoid species whose remains were found several years ago in a cave in South Africa, it had a smaller brain than our direct ancestors, walked upright, and may have used tools.  And, scientists now believe, it lived between 236,000 and 335,000 years ago — which means it would have been alive and kicking when early humans were, too.

mm8345_20150306_134-3The dating of the remains of Homo naledi suggests that the family tree of human beings is a lot more tangled than people once thought.  As scientists focus more and more on searching for fossil evidence of human-like species, they are uncovering new information that reveals a number of different species romping around the pre-historic world.  The Smithsonian page on human ancestry now shows more than 15 early human species.  With so many variations of humanoids, there are bound to be evolutionary dead ends — and, the more human-like remains that are found, the more likely it is that the different offshoots of the evolutionary tree overlapped in time and may have interacted.

Scientists already believe that, around 300,000 or so years ago — or about the same time as the dates suggested for Homo naledi — there were three different offshoots of one of the root humanoid ancestors, Homo heidelbergensis.  Humans remained in Africa, Neanderthals ventured from Africa into Europe, and Denisovans moved east, into Asia.  We know that, for many years thereafter, there was physical interaction between human ancestors and Neanderthals, because many modern humans have a small percentage of Neanderthal DNA.  With three groups of humanoids around, it’s not much of a stretch to imagine Homo naledi existing in that same time frame.   And who knows whether scientists will unearth evidence of other distinct, humanoid species that also date from that same time period?

The intriguing question is:  what happened to those other species?  Did the human ancestors simply prove to be superior in brainpower, body design, tool-making ability, and other attributes that gave them an evolutionary advantage and allowed them to simply out-compete the other species for food, living space, and other conditions that made humans more successful in reproducing . . . or did the early humans slaughter those who were different and drive them into extinction?  Maybe there is a reason that the remains of Homo naledi were found in a cave — they were desperately hiding from our ancestors.

Why Sex Evolved

Scientists are curious people.

Some scientists are trying to determine why sex evolved.  Early life forms had to reproduce somehow, and presumably did so by natural cloning.  At some point in the past, however, sex entered the picture, and now, although some plant and even animal species that still exist reproduce without sex — bananas, starfish, and Komodo dragons are examples — sex has become the dominant method of reproduction.

Scientists wonder why.

7-water-flea-laguna-designGet your mind out of the gutter for a moment.  It’s a fair question, because scientists point out that sexual activity takes time and energy, frequently involves elaborate rituals — dating alone can be both expensive and time-consuming — and is therefore a lot less efficient than cloning.  Organisms that reproduce through cloning (which, incidentally, are entirely female, males not being needed) presumably could reproduce much more rapidly and easily than organisms that used the sexual approach.  As one scientist, Dr. Stuart Auld of the Faculty of Life Sciences of the University of Stirling, put it:  “Sex explains the presence of the peacock’s tail, the stag’s antlers and the male bird of paradise’s elaborate dance. But if a female of any of these species produced offspring on her own, without sex, her offspring should come to dominate, while the other females watch the redundant males fighting and dancing. So, why are we not surrounded by clonal organisms?”

Sex, fighting, dancing, and redundant males.  What could be more interesting than that?

Dr. Auld and his colleagues came up with an ingenious approach to trying to test why sex might have evolved.  They found an organism that reproduces both through cloning and through sex, the common water flea, and they compared offspring of the same mothers that were produced through cloning to those produced through sex.  They found that the sex-produced offspring were much more resistant to disease and parasites than their cloned sisters.  Sex evidently allows the genetic material to be mixed up and also shared, and organisms that use the sex route therefore get an advantage in avoiding illness.

Dr. Auld concludes:  “The ever-present need to evade disease can explain why sex persists in the natural world in spite of the costs.”

So there you have it.

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.
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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?

Where Do Dogs Come From?

The New York Times recently published a fascinating article on ongoing research into the origin of dogs.  By collecting and analyzing the DNA of current dogs and the remains of their long-dead forefathers, scientists are hoping to determine when man’s best friend first appeared on the scene, and where.

When people have thought about the origin of dogs at all, they’ve assumed that dogs are simply domesticated wolves, first developed long ago when hunters shared food with wolves and trained them to become reliant on, and loyal to, humans.  Scientists now believe that’s probably not what happened.  They note that, although dogs and wolves are so closely related they can interbreed, there are important differences in their physiology and especially their behavior.  Some scientists now hypothesize that dogs were, in effect, self-selected, and some variation of ancient wolf began to follow tribes of early human hunter-gatherers because scraps of food were readily available, and became tamer and tamer in their interactions with humans because the friendlier wolves were much more successful in getting food and breeding — which is the ultimate key to evolution.

IMG_0548But where did the domestication process happen, and when?  Most scientists believe it happened 15,000 years ago, and the process was so rapid that by 14,000 years ago people were burying dogs, sometimes along with humans.  Others believe that dogs are much older and that the domestication may have occurred as long as 30,000 years ago.  As for where dogs first developed, the candidates range from Europe to Africa to Siberia.  To try to answer some of the questions, scientists are collaborating on a vast world-wide DNA collection process and are hoping that, if they assemble enough data, they may be able to trace origins and find useful clues to answer these questions.

They are important questions, and not just for the dog lovers among us.  (In fact, one of the scientists involved in the project, far from being a warm and fuzzy dog fan, contends that the modern house dog “may have evolved into a parasite.”)  The period of human evolution from 30,000 to 15,000 years ago is shrouded in mystery, but clearly something was happening as humans progressed from roving bands of hunter-gatherers to multi-family tribes that formed settlements, built permanent structures, grew crops, and eventually created the first cities and organized civilizations.  It is not far-fetched to speculate that the training and domestication of dogs, and their assumption of their familiar roles of protector, fellow hunter, and treasured friend, may have been an important part of that settling down process.  Those of us who have and love dogs certainly can attest that there is a strong bond between humans and canines and that, in many respects, the bond makes dog owners better people.

Where did Kasey, and Penny, and Dusty and George before them, come from, and how did their distant ancestors affect the development of human culture?  I’d like to know.