About 60 million years ago, at least one group of mammals left the ground to forage for insects, and indeed live, in trees. Life in the trees involved several changes. Movement in three dimensions, especially on delicate tree limbs, requires increased dexterity and range of motion. Chasing after food in the canopy, especially if accompanied by leaping from place to place, needs exceptionally good agility and vision. In trees, hanging on is essential, and it can be done in several different ways. Good sharp claws, such as those found in cats and squirrels, is one way. Primates took another tact altogether. They abandoned claws and, instead, wrapped newly evolved opposable thumbs around branches. Not only do opposable thumbs give a strong grip, but they also allow for delicate manipulations needed for plucking food and carrying it toward the mouth.
Upright posture is not common, even among primates that spend much of their time climbing up and down tree trunks. When not climbing, most primates can be found standing on all four limbs. One group, the hominoids, can often be found resting sitting upright. As easy as it seems to us, this change in posture required quite a number of modifications in the body from that found in other primates. The position of the eyes in the skull had to rotate, or hominoids would be perpetual stargazers. The chest cavity became flatter, thereby placing more weight straight above the hips, and the pesky tail, likely to forever be annoyingly in the way when sitting, was reduced to a stump.
Although primates were entrenched in an arboreal existence, at least one hominoid group decided to return back to its early mammalian roots and set its hind feet firmly on land. The hominid ancestors of man were bipedal and had a reoriented vertebral column and skull to accommodate this new vertical stance. Tool construction and use flourished and the passage of genetic information for survival, from one generation to another, was heavily supplemented with cultural training. Knowledge became power and an increased brain size allowed for the gathering and synthesis of more knowledge.
The exact beginning of modern man is a point still being debated. Some argue that the real starting point is reflected by a sophisticated use of tools that is only found in those few who have mastered the art of dry-fly presentation.
Others take a more liberal view and include the rest of us living today. Although anatomical clues make it possible to distinguish us from our close relative, Neandertal man, the behavioral and cultural differences appear to be few and subtle. Modern humans may have their origins when the two forms commingled their ideas and discoveries before Neandertals eventually disappeared.

All Text © Dr. Carl Ferraris

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