Have you ever wondered how archaeologist can learn so much from studying skeletons?
Determining Age with Bones
Most of the bones in humans develop from cartilage that resemble the bones they will become. As people grow, their bones get longer and thicker and the cartilage is replaced by bone. If cartilage can be seen at the ends of bones, there will be no further growth and if no cartilage is present, the person has reached full maturity.
All during life, minerals are deposited and removed from the bone. During childhood and adolescence, the deposit of mineral occurs faster than the mineral loss, and the bones grow. The average female grows until 18 years of age and males continue to grow to 20 or 21 years of age. Between the years of about 18 to 35, there is a balance of mineral deposit and loss, so bones stay a constant size. After age 35, bone loss exceed bone gain.
In adults, the ends of the rib bones gradually change shape over the years. The sternal ends are rounded in young adults and become more cup-shaped and jagged with increasing age.
The skulls of adolescents and children are quite different than those of adults. At birth the bones of the head are not fused together as they are in adults. Instead they are separated by membranous areas called fontanelles or soft spots. These allow some movement between bones so that the skull can be compressed as it pass through the birth canal. As a child grows, the fontanelles allow the brain to also grow as the bones slowly grow together and eventually fuse in adulthood.
In youth the pelvic girdle consists of three bones: ilium, ischium and pubis, which eventually fuse to for the pelvic girdle. This pelvic girdle serves as an area of attachment for the bones and muscles of the legs.
Male or Female Bones?
Females have wider pelvises than males to make childbirth possible, so the arch is wide and the bones are lighter and smoother. The female sacrum (large, triangular bone at the base of the spine) is wider and shorter than the male's. In a female, the coccyx (or tail bone) is more movable than in a male.
You can also tell whether a skeleton is male or female by looking at the skull. The female skull is rounder and smaller than the male's. The female forehead is longer vertically and the jaw is smaller.
In males, expansion of the ribcage is caused by the effects of testosterone during puberty. Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen. The sternum or breastbone is a long flat bone located in the center of the chest. Male sternums are noticeably larger than female.
I gave the boys pictures of bones and had them determine whether they were adult or child bones and whether they were male or female. Can you tell which they are from looking at the pictures?
Source: Crime Scene Investigations, Real-Life Science Labs For Grades 6-12 by Pam Walker and Elaine Wood