Chimpanzees are our closest living relatives. Biologists have found that the DNA in the cells of humans and chimpanzees is about 99% the same. This close relationship exists also between horses and zebras, grizzly and polar bears. We would never mistake chimpanzees and humans because their external appearances (phenotypes) are distinct. By studying skeletal differences, paleontologists can determine if a fossil bone is from a human or a chimp… Here are some clues:

· The modern human brain is more than three times larger than the chimpanzee. The cranial capacity is about 400 cc for the chimp and about 1400 cc for humans.

· The foramen magnum (opening at the base of the skull) is where the spinal cord enters the skull. In the chimpanzee, this opening is located towards the back of the skull; in humans it is found closer to the middle of the skull base.

· Human canine teeth, the third tooth from the center on each side, are considerably smaller than those of the chimpanzee.

· Chimps have longer and more curved fingers for climbing in trees and knuckle-walking. The human thumb is relatively straighter and longer than the chimp's.

· Human and chimpanzee trunks are about the same size.

· The chimp rib cage is triangular and narrow at the shoulder.

· The clavicle or collar bone angles upward towards the shoulders in the chimpanzee, giving the appearance of no neck.

· The human pelvis is shorter than the chimp's.

· The femur or thigh bone is longer in humans.

· The chimpanzee footprint shows long, curved toes with the big toe divergent or pointing away from the other toes. This makes it more useful for grasping. The human footprint has a big toe that is convergent or pointing in the same direction as the other toes. This convergence allows the feet to better support the body's weight.

Your group will act as paleontologists at the African location where recent erosion has exposed many fossil bones. It appears that the fossils come from two different species but are mixed together. Your job is to carefully examine the fossil bones and classify them into either the human species (Homo Sapiens) or the chimpanzee (Pan troglodytes).

Carefully empty the bones from envelope #1 and sort them into two columns on your desk - chimpanzee or human. Place your results in the chart following.

Your team has just stumbled across another set of fossils which is neither human or chimpanzee. Using your expert knowledge of humans and chimps you begin to analyze these new bones.

Open Envelope #2 and compare each of the new fossils to the chimpanzees and the human. Using a chart, rate each new bone as either: similar to chimpanzee, similar to human, human, chimpanzee or similar to both. Include the following information:

1. What is the significance of this fossil?

2. Suggest a name for this fossil.

By comparing the amino acid sequences in homologous proteins of similar organisms and of diverse organisms, evolutionary relationships can be determined. Biologists agree that that the greater the similarity between the amino acid sequences of two organisms, the closer their relationship. Conversely, the greater the differences, the more distant the relationship.

Examine the chart below which compares corresponding portions of hemoglobin molecules in humans and five other vertebrate animals. Hemoglobin, a protein composed of several long chains of amino acids, is the oxygen-carrying molecule in red blood cells. The sequence shown is only a portion of a chain made up of 146 amino acids.

Create a chart that records the number of amino acid differences and the positions in which they vary when compared to humans.

1. Based on your results, which animal appears to be most closely related to humans? Which one is least closely related? Explain.

2. Click on the site, Becoming Human, and go to the Learning Center. Complete the following questions:

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