Origins of Us – Bones: In the first episode, Dr Alice Roberts looks at how our skeleton reveals our incredible evolutionary journey. Trekking through the forests of our ancient ancestors, she goes to meet the apes who still live there today – chimpanzees. In six million years we have become very different, and what kick-started this can be found in an extraordinary fossil – Sahelanthropus. A single hole where the spine was attached suggests that our ancestors started the journey to being human by standing upright. We take it for granted, but standing up and walking is surprisingly complex – each step involves the co-ordination of over 200 muscles.
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Charting the major advances from Australopithecus to Homo erectus and beyond, Alice tells the epic story of human evolution through our body today. New research has uncovered clues in our ankles, waists and necks that show how our ancestors were forced to survive on the open plain – by walking and running for their lives. From the neck down we have inherited the body of our ancestor Homo erectus, who lived on the plains of Africa nearly two million years ago.
Finally Alice looks at probably the most important advance in our evolutionary story. A fortuitous by-product of standing up was freeing up our hands. With pressure-sensitive gloves, she demonstrates how the tiniest of anatomical tweaks to our thumbs and little fingers transformed hands that evolved to grasp branches into ones that could use tools. And with our dexterous hands, our species, Homo sapiens, would change the world.
Origins of Us – Bones
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions.
Bone tissue (osseous tissue), which is also called bone in the uncountable sense of that word, is hard tissue, a type of specialized connective tissue. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Osteoblasts and osteocytes are involved in the formation and mineralization of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralized matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts. Bone tissue is mineralized tissue of two types, cortical bone and cancellous bone. Other types of tissue found in bones include bone marrow, endosteum, periosteum, nerves, blood vessels and cartilage.
In the human body at birth, there are approximately 300 bones present; many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones. The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.
