Earth Science: Mammals – Humans
Modern humans, Homo sapiens, are distinguished from other living things by several physical characteristics and by the many intellectual and cultural achievements of several millennia.
No other living creature looks, lives, or moves like a human being. The evolution of humans has been supported by changes in the skeleton in response to changing conditions and demands. Today, the pelvis is broad and tipped forward. The human backbone forms an S-shape, which absorbs vertical forces and allows for a wide range of upper torso movements.
The big toe does not grip like those of the great apes; it lies parallel to the foot, which makes it easier to balance and move standing up. The arching bones in the sole of the foot provide cushioning during upright walking. The hands have changed dramatically, as they are no longer required to assist movement.
With an opposable thumb and a rotating forearm, the human hand is an ideal tool for exploration, grip- ping, and manipulation.
Over the course of human development, the skull expanded and the face flattened, ridges over the eyes disappeared, and the nose and chin became more prominent.
Body hair dramatically reduced in volume and coverage, and the teeth became smaller and more suited to a varied diet. The evolution of a moveable tongue, arched palate, and appropriately positioned larynx were critical to enabling the development of spoken language.
Intellectual and cultural development
Human physical and intellectual developments are closely related. Childhood lasts longer for humans than for chimpanzees, partly because humans are born at an earlier stage of development. Because of this, a significant part of brain development occurs after birth.
In addition, the human brain has enhanced folds, which make efficient use of the space within the cranium. The larger brain has led to greater intelligence, an aptitude for language, and an ability to learn and engage in complex social behaviors—all crucial preconditions for the development of complicated languages and the emergence of human culture.
TOOLS
Among the first tools used by early humans were stone axes, which appeared some 1.5 million years ago.
With a rounded side for holding and a sharp edge chipped away on both sides to form a blade, it could be used for cutting, chopping, or scraping. This basic model was then further developed and refined.