• How are human proteins similar and different to other primates? 
• Can the differences show evolutionary trends? 

Overview of Comparing Primate Proteins

 This change has lead us to a great number of questions. When did these changes occur and what is the path that shows our ancestral form’s genealogy? Who were our direct ancestors and what are the side branches? When did this branching occur? Can we learn about the past history of our species by comparing modern organisms to man?

 Biologists have begun to use sequences of amino acids in proteins and nucleotide sequences of DNA as an evolutionary clock. Those organisms which have more alterations in their protein sequences are being classified farther away from other organisms in an evolutionary sense when compared to those with more common sequences. In the past Biologists and Paleontologists have used fossils, homologous structures and comparative embryology to help classify organisms and also to try to determine how closely related two organisms actually are.

 Scientists have found that certain kinds of protein in different primate species contain many of the same sequences of amino acids (a property called conservation). Also organisms that are similar, seem to have similar biochemistry such as hemoglobin sequence and structure. The similarities of these proteins indicate similarities in the DNA of the organisms. Scientists believe that the more closely two species DNA are, the more closely related they must be. There seems to be a correlation between the number and types of differences and to the phylogenic "closeness" of the organisms compared. 

DeVries theory of mutations provided an explanation as to how the variations within a species could occur. Changes in the sequence of the hereditary material (DNA nucleotides) lead to alterations in the structures and functions of the organism ( or protein). Some changes were bad and lead to disorders or death, some had no effect as the actual protein sequence was left unaltered and a rare few mutations actually made the organism better at competing in their environment. 

Those organisms who survive and reproduce are evolutionarily successful. And, those members of the population with better adaptations survive more frequently and pass on those successful traits. Thus the species changes (or evolves) as it becomes more and more like the surviving population. Finally, over time the population may acquire enough differences that it is no longer capable of reproducing with other organisms like the original species type. The history of Homo sapiens has shown this accumulation of differences since it diverged millions of years ago from other primate forms. 

Manual Amino Acid Analysis

 1. Figure 1 shows the amino acids found in selected sites in hemoglobin of different vertebrates.

 Figure 1: Selected amino acid positions in the Hemoglobin of some vertebrates. 

2. Count the number of molecules of each amino acid in human hemoglobin. (Don't miss the second section of data). Record these totals in the appropriate column of Data Table 1.

 3. Count the number of molecules of each amino acid of other vertebrates hemoglobin. Record these totals in the appropriate columns of Data Table 1.

 4. Going from left to right, note the position of each amino acid. Count the numbers of similarities in the amino acid positions in human hemoglobin as compared with the hemoglobin of the other vertebrates in figure 1. Record your observations in Data Table 2.

 5. Reexamine figure 1 and count the numbers of differences in the amino acid positions in human hemoglobin as compared with the hemoglobin of the other vertebrates in figure 1. Record your observations in Data Table 2.

 Observations:

 Data Table 1:
 
 

Analyzing your Observations:

1. From your observations in data table 2, which primate is most closely related to the human being? 
2. Which primate is most closely related? 
3. From your observations in data table 2, which non-primate is most closely related to the human being? 
4. Which non-primate is most closely related? 

Comparing Primate Features

Part B . Comparing the skull characteristics, brain capacity, teeth, hands and skeletons.

1. Determine the brain area, face area, ratio of brain to face area, cranial capacity, jaw angle, distance across back of jaw, distance across front of jaw, ratio of back to front distances, number of teeth, number of each type of tooth, sagittal crest, and brow ridge. Record the answers in data table 3.

Primate Skulls

Data Table 3

Analysis:

1. How do Australopithecus and Gorilla compare in terms of cranial capacity, lower jaw shape and jaw angle?
2. Which traits in question 1 does Australopithecus seem to share with homo Sapien?
3. Using face to brain area ratios, does Australopithecus more closely resemble Gorilla or Homo Sapien?
4. List the traits used in this lab that are similar in Australopithecus and Homo Sapien.
5. List the traits used in this lab that are similar in Australopithecus and Gorilla.
6. List the traits used in this lab that are similar in Gorilla and Homo Sapien.
7. Explain the differences in face to brain ratios, jaw angles, and jaw shapes in the three skulls.
8. Place the three primates in order from smallest to largest brain capacity.
9. What primate has the largest brain capacity?
10. How might a large brain help humans function and communicate with others?
11. Describe the similarities and differences of each primate hand.
12. What advantages might an opposable thumb have?
13. Compare the skeletons. What are some similarities and differences? Which of the two skeletons can you conclude is bipedal? What is one advantage of this condition?

Conclusions:

1. From your data , which primate is most closely related to the human being? Which is least closely related? Support your conclusions from the data above.
2. Which nonprimate vertebrate listed is most closely related to human beings? Which is least closely related? Support your conclusions from the data above.