Lab Report
Updated: 2005

Demonstration of a close genetic relationship between human and chimpanzee through the Nutall precipitation reaction


Some scientists theorize that humans and chimpanzees evolved from a common ancestor millions of years ago. Because of this theory, we hypothesized that the chimpanzee blood proteins would most resemble human blood proteins. Three other vertebrates, the frog, cow, and monkey were also compared in this study. In order to test for similarities in various blood proteins, the Nutall Precipitation process was used. By employing this technique, we noted and compared the agglutination of red blood cells from the five species. This method allowed us to see which animal’s blood proteins would be most closely related to humans. Results confirmed our hypothesis: the blood proteins of chimpanzees are most closely related to human blood proteins, more so than to the blood proteins of a cow, a frog, and a monkey.


The Nutall Precipitation is a technique used to test and compare the relationship of the blood proteins between one species and another to see how they are similar or different. The Nutall Precipitation capitalizes on the vertebrates’ immune defense mechanism, which resists foreign materials that are introduced into their blood (Braun, pp. 71). To combat the foreign materials, the vertebrates will develop antibodies which, in turn, will agglutinate to the foreign material. The agglutination causes a fast precipitation reaction (Braun, pp. 71). By judging the agglutination amounts, we can determine if the materials are more or less foreign to the blood. The Nutall Precipitation can attempt to prove or disprove the hypothesis that the chimpanzee is the animal that is most closely related to a human. An anti-human serum was introduced into the blood proteins of the chimpanzee, cow, frog, and the monkey. The agglutination reactions allowed us to determine which of the four animals was the one most closely related to a human. When there is an increase in agglutination between the animal and human blood, it signifies that the two species’ blood is more similar, thus showing a closer relationship. When the agglutination is lighter, it signifies that the blood proteins in human blood and animal blood are less similar, thus determining that the two species are not as closely related. In our experiment using the Nutall Precipitation, our hypothesis that the chimpanzee is the animal most closely related to humans was tested to determine whether or not the chimpanzee’s agglutination with the human blood is greater than with the other species-the cow, frog, and the monkey.


The Nutall Precipitation technique tested the hypothesis-five dishes were set up, each one with a different serum from a chimpanzee, cow, frog, monkey, and a human. The dish with the anti-human serum was compared with the four dishes of animal serum. In each dish, there were eight wells containing serial dilutions of a specific animal serum (50 – 300 l) and a combination of water (100 – 350 l) and anti-human serum (400 l). Data was recorded based on the amount of agglutination in each dish. A table chart was developed, using the rubric scores of 0, 1, 2, and 3. A score of 0 signified that there was no reaction between the anti-human serum and animal serum. A score of 1 indicated that there was a reaction, but that it was light and weak. A score of 2 meant that there was a medium reaction, showing signs of agglutination. A score of 3 signified that there was high agglutination with a strong and immediate reaction.

Results and Discussion

Well Number:

1 2 3 4 5 6 7 8
Human 3 3 3 3 2 2 1 1
Cow 2 2 1 1 1 0 0 0
Chimpanzee 3 3 3 3 2 2 1 1
Frog 1 1 0 0 0 0 0 0
Monkey 3 3 2 2 2 2 1 0

Based on the recorded data, the dish containing the chimpanzee serum showed an immediate and strong reaction with the human’s anti-serum with the heaviest agglutination in comparison to the other species. In fact, the dishes containing the chimpanzee’s serum and the anti-human serum showed the same amounts of agglutination. The monkey was shown to be trailing the chimpanzee, with the cow next. The frog showed the least amount of agglutination, with wells 3 through 8 showing no signs of agglutination. The conclusion strongly indicates that the sera of the chimpanzee and humans showed very similar agglutination reactions with the anti-human serum. This supports our hypothesis that the chimpanzee blood protein is the most closely related to the human blood protein as compared to the blood proteins of a cow, a frog, and a monkey.


Braun DC and Pearce LL, Laboratory Manual for Introduction to Biology. 5th ed. Washington (DC): Gallaudet University; 2004: 69 – 75

Olson MV and Varki A. Sequencing the chimpanzee genome: insights into human evolution and disease Nature Reviews Genetics. 2003 Jan 01;4:20-28.

****This sample biology lab report was developed by Will Garrow for a biology course at Gallaudet University. It was revised by Raymond Merritt and Jane Dillehay of the Department of Biology.

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