A skeleton is…
A team of Northeast Ohio researchers announced a rare and important find – the partial skeleton of a 3.6 million-year-old early human ancestor belonging to the same species as, but much older than, the iconic 3.2 million-year-old Lucy fossil discovered in 1974.
Less than 10 such largely intact skeletons 1.5 million years or older have been found. Greater Cleveland researchers have played leading roles in three of those discoveries, reinforcing the region’s prominence in the search for humanity’s origins.
The new specimen is called Kadanuumuu (pronounced Kah-dah-NEW-moo). The nickname means “big man” in the language of the Afar tribesmen who helped unearth his weathered bones from a hardscrabble Ethiopian plain beginning in 2005.
“Big” is an apt description of both Kadanuumuu’s stature and his significance. The scientists who analyzed the long-legged fossil say it erases any doubts about stubby Lucy and her kind’s ability to walk well on two legs, and reveals new information about when and how bipedality developed.
“It’s all about human-like bipedality evolving earlier than some people think,” said Cleveland Museum of Natural History anthropologist Yohannes Haile-Selassie,
“Many dozens of A. afarensis fossils have been uncovered since Lucy was discovered in 1974, but none as complete as this one. Kadanuumuu’s forearm was first extracted from a hunk of mudstone in February 2005, and subsequent expeditions uncovered an entire knee, part of a pelvis, and well preserved sections of the thorax.
“We have the clavicle, a first rib, a scapula, and the humerus,” says physical anthropologist Bruce Latimer of Case Western Reserve University in Cleveland, Ohio, one of the co-leaders on the dig. “That enables us to say something about how [Kadanuumuu] was using its arm, and it was clearly not using it the way an ape uses it. It finally takes knuckle-walking off the table.” At five and a half feet tall, Kadanuumuu would also have towered two feet over Lucy, lending support to the view that there was a high degree of sexual dimorphism in the species.”
– Archaeology, “Kadanuumuu” – Woranso-Mille, Ethiopia Volume 64 Number 1, January/February 2011 by Brendan Borrell
“The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate. In humans, it consists of 80 bones and is composed of eight parts; the skull bones, the ossicles of the middle ear, the hyoid bone, the rib cage, sternum and the vertebral column. ”
The human skull
What are bones made of?
Although bones in museums are dry, hard, or crumbly, the bones in your body are different. The bones that make up your skeleton are all very much alive, growing and changing all the time like other parts of your body. Almost every bone in your body is made of the same materials:
The outer surface of bone is called the periosteum (say: pare-ee-OS-tee-um). It’s a thin, dense membrane that contains nerves and blood vessels that nourish the bone.
The next layer is made up of compact bone. This part is smooth and very hard. It’s the part you see when you look at a skeleton.
Within the compact bone are many layers of cancellous (say: KAN-sell-us) bone, which looks a bit like a sponge. Cancellous bone is not quite as hard as compact bone, but it is still very strong.
In many bones, the cancellous bone protects the innermost part of the bone, the bone marrow (say: MAIR-oh). Bone marrow is sort of like a thick jelly, and its job is to make blood cells.
Bone marrow makes blood cells
How many bones do humans have?
A baby’s body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. Some of a baby’s bones are made entirely of a special material called cartilage (say: KAR-tel-ij). Other bones in a baby are partly made of cartilage. This cartilage is soft and flexible. During childhood, as you are growing, the cartilage grows and is slowly replaced by bone, with help from calcium.
By the time you are about 25, this process will be complete. After this happens, there can be no more growth — the bones are as big as they will ever be. All of these bones make up a skeleton that is both very strong and very light.
This is a human hand from the outside – my own, after a hiking “incident” 😉
This is an X-ray of the same hand; the doctors were making sure that none of my bones were broken. (None were, although there was some damage to the tissues.)