To learn about where we've been and where we're headed, we look to our closest living brethren: nonhuman primates. Biologically speaking, we share roughly 96 percent of our DNA with chimpanzees, our closest living great ape cousins today [source: National Human Genome Research Institute]. But while we have much in common with other primates, we're still somehow different.
So what makes humans so special? Why are Homo sapiens rather than other primates driving cars and developing cures for disease?
In the past century especially, we've only begun to answer these questions. The study of primates -- also called primatology -- is a behavioral, historical and medical endeavor. We examine primates not only in their natural habitats, but we also analyze them in labs and sanctuaries, where they continue to further our understanding of their lives and our own. Whether we're looking for the origins of language and higher thought or trying to understand how the human body works, primates are invaluable contributors to our search for answers.
Though we often consider ourselves to be intelligent and advanced, it's important to acknowledge that we're not necessarily better or more "evolved" than other primates. Just as our ancestors withstood Mother Nature to perpetuate our species, primates and their ancestors have adapted to survive and deserve our respect.
Humans aren't the only ones who use two feet to get around. Read about what we've learned by studying locomotion in primates on the next page.
10: Possible Origins of Bipedalism
One of the most obvious differences between humans and nonhuman primates is the way we move around. Generally speaking, humans walk on two legs (a term called bipedalism). Nonhuman primates walk on all four limbs on the ground with their palms or knuckles, grasp or hang on trees -- or a combination of these movements [source: Prost].
But when and where bipedalism emerged isn't exactly clear. Some scientists who study modern humans' ancestors, or hominins, analyze fossils to find out whether our ancestors walked on two feet. To complement this approach, researchers have also studied living primates to learn how body structure and the environment allowed human ancestors to walk [source: Capitanio].
A type of chimpanzee, called a bonobo, and Japanese macaques shed light on this issue because they occasionally move bipedally to carry objects or can be trained to walk on two feet [sources: D'Août et al., Nakatsukasa et al.]. Although this type of bipedalism isn't identical to that of humans, it gives us a starting point to look at the circumstances in which bipedalism has adaptive benefits and at what energetic costs [sources: D'Août et al., Nakatsukasa et al.].
How do nonhuman primates help us learn about our own bodies? Check out the next page to find out.
9: Genetics and Human Biology
By studying the genetics and general biology of nonhuman primates, we've been able to look at our relationships with animals and with one another. Though the roundworm takes the cake as the first animal to have its entire genome, or genetic code, sequenced, researchers have worked at sequencing the genome of certain primate species in tandem with humans [sources: National Human Genome Research Institute, 1998, National Human Genome Research Institute, 2010]. This type of work not only gives us a better sense of our place in the animal kingdom, it also opens the door for scientists to study genetic diseases that may be present in other primates.
Knowledge from studying nonhuman primates has also enabled anthropologists to use genetic tools to determine the behavioral and physical qualities of early humans, or hominins. In fact, some have even begun to parse through the genome of Neanderthals, one of humans' closest hominin ancestors, by extracting DNA from fossils. From analyzing the genetics of fossils and bones of Neanderthals, we've learned so far that our DNA and that of Neanderthals are 99.5 percent identical [source: Noonan et al.].
In order to learn more about human biology and develop treatments for diseases, scientists use what they know about primate biology to develop new approaches -- something we'll learn more about in coming sections.
Next up, we'll examine primate social groups and what we've learned about human communities by studying them.
8: Insight into Group Sociality
You may not think humans and a group of monkeys grooming each other have anything in common, but the truth is we have much to learn from studying primates' group dynamics. Sociality in primates reinforces relationships and can even promote peace amid a fight, much in the same way social bonds and certain behaviors help humans make amends [source: de Waal]. Through studying group structure and complex social relationships, we've learned that human ancestors may have acted similar to primates -- grooming and all [source: Nakamura].
We've also learned about factors that may limit human group size. One analysis found a relationship between the size of the neocortex portion of the brain and group size in several nonhuman primate species [source: Dunbar]. Group size was measured as the number of individuals someone can actively know and maintain a relationship with. We've applied this concept to humans to determine what our average group size should be. According to Dunbar, it should be somewhere around 150 people. Even though these findings are intriguing, it's hard to find other ways to reinforce this idea.
Another facet of group sociality is dominance hierarchies, or rigid class levels within a group. Depending on the species of primate, some groups are led by males while others are dominated by females. Group dynamics are important in piecing together what social groups in early humans looked like.
Like us, primates use tools to make life easier. Read what we've learned from them next.
7: Possible Origins of Tool Use
Today we use high-tech tools to track primates in the wild and study their biology and behavior. But how did humans come to study nonhuman primates, and not the other way around?
The ability to alter the environment for adaptive purposes makes humans and primates special, yet humans have taken this concept to the extreme. Researchers hypothesize that tool use was a game-changer for early humans since it allowed them to hunt and process different foods. Some researchers even speculate that accessing these new foods led to an increase in brain size and altered group dynamics, which may have changed how ]early humans communicated with one another [source: Aiello and Wheeler].
To understand how tool use came about, we turn to other primates again. We have plenty of examples to draw from -- including chimpanzee termite "fishing," nut-cracking with stone tools in capuchin monkeys and chimpanzees, and the use of sticks to gather food by orangutans -- to list a few [sources: Morelle, van Schaik et al.].
Like other areas studied in human evolution, primate tool use shows us when and where tool use is possible for animals that share similar cognitive and morphological traits with humans. In addition to piecing together what made human ancestors pick up tools in the first place, we're also discovering the innovative ways these animals adapt to their environments.
Read on to find out how our knowledge of primates led to a ground-breaking discovery in biology.
6: Stem Cell Technology
The development of human embryonic stem cells in the 1990s revolutionized how scientists approached new medical treatments to combat certain cancers and diseases. Did you know that this discovery was first developed using the cells of nonhuman primates?
Before scientists applied their technique to human embryos and other types of regenerative cells, they created stem cell lines from cells of rhesus macaque monkeys (a type of monkey found in Asia) and common marmosets (a species of monkey from Brazil) [sources: Thomson et al., 1995; Thomson et al., 1996]. These studies occurred in vitro, which means certain cells were taken from the animal and grown in a lab. Without the knowledge of cell differentiation -- or the ability of a general cell to change itself to act as a more specific type of cell -- in primates, researchers would not have been as successful in crafting stem cell technology for humans.
Today these same developments have been used to produce induced-pluripotent stem cells, which usually come from adult cells and not from embryos. In its infancy, stem cell technology shows promise for patients living with medical conditions ranging from Parkinson's disease to diabetes and arthritis [source: Stem Cell Information].
Both humans and nonhuman primates learn from and teach friends and family new skills. Keep reading to learn how we benefit from comparing the two.
5: Learning and Cognition
While watching great apes such as chimpanzees, gorillas and orangutans teach their young new skills and behaviors, we can't help but see similarities to humans.
For example, we've learned that young primates learn from their mothers much in the same way children learn from their parents. Both groups learn through imitating older individuals -- particularly mothers [source: Myowa-Yamakoshi et al.]. In addition, analyzing how primates actively teach other members of their group a specific task sheds light on how early humans may have passed on skills necessary for survival.
Our understanding of primate cognition has allowed us to explore what makes us human as well. One concept called "Theory of Mind," or the ability to acknowledge that you and the people around you have different mental states -- is studied often in nonhuman primates [source: Premack and Woodruff]. Though we'll never know the innermost thoughts of primates, many researchers claim testing Theory of Mind can help us set ourselves apart from our primate relatives.
The Gallup mirror test is another method used to determine self-recognition. Here, researchers test whether an animal notices itself in the mirror after a visible marking is applied to the face [source: Gallup, 1970]. Children eventually realize the reflection in the mirror symbolizes them at a young age, and we've learned that some primates do this as well [source: Gallup, 2005].
Like humans, primates also pass down unique behaviors from one generation to the next. Find out more on the next page.
4: Cultural Transmission
We know culture and language are passed on from one generation to the next, but we've learned many of the basics from primates. Although our definitions of culture may be different than the behaviors we see in animal groups, we're gradually learning that primates have concepts of culture, too.
Different from instincts, these behaviors vary from group to group -- much like how traditions in societies differ around the world. To look at how culture may have been transmitted in human ancestors, we study primates that seem to carry on their own traditions [source: McGrew]. This idea is especially compelling when neighboring groups of the same species use different methods to achieve the same outcome. As we discussed in the previous section, learning in social contexts is especially important to both humans and nonhuman primates, but passing on these traditions is what makes certain animal societies unique.
Finding out how culture spreads is one thing, but pinpointing its origins is another. We'll move on to the origins of language on the following page.
3: Possible Origins of Language
We often learn about the origins of spoken language by looking at how primates communicate with one another. Nonhuman primates cannot talk like humans, but that doesn't mean they can't communicate with members of their group or even with us.
A bonobo named Kanzi, for example, was raised in captivity and interacted with humans and other bonobos. Researchers working with Kanzi noticed that he began to pick up on the meaning of words and symbols when he was exposed to them growing up [source: NOVA]. Eventually, he learned to use a lexigram panel with symbols to create responses and express his thoughts. Kanzi has helped us learn that the level of communication we enjoy isn't necessarily limited to humans, and that human ancestors who were not able to communicate verbally could have still conveyed messages to one another through body language and symbols.
Shrieklike alarm calls in nonhuman primates have also contributed to our knowledge of how our ancestors may have communicated before language. For instance, vervet monkeys give off different alarm calls depending on the type of predator in the area [source: Seyfarth et al.]. Once a monkey vocalizes to other members of its group after seeing a leopard, the other monkeys will head for the trees. In another situation, if a monkey alerts his group after seeing a predatory bird in the sky, members of the group will move down to the ground. From this, we can hypothesize how early humans warned one another of potential threats.
In addition to studying primates in the wild, we also study them in lab settings to advance modern medicine. Check out the next page to learn which biomedical developments can be credited to primates.
2: Discoveries in Medicine
We've also learned a good deal from primates by studying them in the lab. Along with other animals, primates are routinely used to develop and test treatments for diseases and medical conditions. The use of primates in research is a controversial topic, especially among animal rights activists who believe it isn't ethical. It's important to understand that using any vertebrate animal in research is regulated at the federal level.
What have we learned from using studying primates in a biomedical setting?
For starters, primates were used to test the effectiveness of a polio vaccine, which drastically reduced the disease in the 20th century. Today, researchers still learn about basic immune responses in humans by studying viruses and diseases in nonhuman primates [source: National Primate Research Centers].
Over the years, a range of treatments and basic developments have resulted from studying primates, including:
- Insulin treatments for people living with diabetes
- Safer techniques for heart, eye and bone surgeries
- Better medical care for prenatal and postnatal infants
- Ways to study how diseases develop and progress
- Treatments for polycystic ovary syndrome and endometriosis in women
- Discovery of the Rh blood incompatibility in infants and mothers
Can primates make love and war like humans? Read more about how primates teach us about our own humanity on the next page.
1: Human Nature
As human beings, we want to understand the larger questions in life. Why do we fall in love? What causes war and fighting? Where do we fit in the grander scheme of things?
To explore these questions, we compare our sense of humanity to that of other primates. Over the years, scientists have discovered that primates act altruistically, express empathy and even seem to mourn the loss of deceased friends [source: Barley].
We've learned that primates find ways to avoid and resolve conflicts -- much like humans -- through food sharing, mating and giving out favors [sources: Flack and de Waal, Palagi et al.]. Since these conscious decisions aren't typically observed in other animals, scientists think the origins of human nature lie deep in our primate past.
We've studied chimpanzees and bonobos closely to explore our feelings of love and conflict. For example, both male and female bonobos use sex to dissipate tension in a group, whereas chimpanzees are known to patrol their territories and sometimes fight members of neighboring groups to the death [source: de Waal].
Despite studying primates to learn about ourselves, we're faced with the fact that nearly half of the world's primate species face extinction -- a trend caused primarily by human activity [source: International Union for Conservation and Nature]. Ultimately, our ability to continue studying primates in the future depends on how well we will protect them today.
For more resources on studying primates, head over to the next page.
Lots More Information
- 5 Most Cloned Animals
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- 10 Finds that Define Human Evolution
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- Aiello, L. and Wheeler, P. "The expensive-tissue hypothesis: the brain and digestive system in human and primate evolution." Current Anthropology. 36, 2. 199-221. 1995. (Dec. 9, 2010) http://isites.harvard.edu/fs/docs/icb.topic514568.files/Aiello_Wheeler_The%20Expensive%20Tissue%20Hypothesis.pdf
- Barley, Shanta. "How chimps mourn their dead." The New Scientist. April 26, 2010. (Dec. 10, 2010). http://www.newscientist.com/article/dn18818-how-chimps-mourn-their-dead.html
- Capitanio, John. "Research Questions and Answers." American Society of Primatologists. July 20, 2008. (Dec. 1, 2010). http://www.asp.org/research/faq.html
- D'Août, K., Vereecke, E., Schoonaert, K., De Clercq, D., Van Elsacker, L., and Aerts, P. Locomotion in bonobos (Pan paniscus): differences and similarities between bipedal and quadrupedal terrestrial walking, and a comparison with other modes of movement. Journal of Anatomy. 2004. (Dec. 2, 2010) http://www.ncbi.nlm.nih.gov/pubmed/15198700
- de Waal, F. "Chimpanzee politics: power and sex among apes." The Johns Hopkins University Press. 2007.
- Dunbar, R. I. M. "Neocortex size as a constraint on group size in primates." Journal of Human Evolution. 22, 6.
- Flack, J. and de Waal, F. "'Any animal whatever': Darwinian building blocks of morality in monkeys and great apes." Journal of Consciousness Studies. 7, 1 & 2. 1-29. 2000. (Dec. 11, 2010) http://www.emory.edu/LIVING_LINKS/pdf_attachments/Flack_deWaal_moral.pdf
- Gallup, G. "Chimpanzees: self-recognition." Science. 167, 3914. 1970. (Dec. 9, 2010) http://www.sciencemag.org/content/167/3914/86.abstract
- Gallup, G. "Self-awareness and the emergence of mind in primates." American Journal of Primatology. 2, 3. 237-248. 2005. (Dec. 9, 2010) http://onlinelibrary.wiley.com/doi/10.1002/ajp.1350020302/abstract
- "Government and Professional Resources: Animal Welfare Act." U.S. Department of Agriculture. Nov. 4, 2010. (Dec. 7, 2010). http://awic.nal.usda.gov/nal_display/index.php?info_center=3&tax_level=3&tax_subject=182&topic_id=1118&level3_id=6735&level4_id=0&level5_id=0&placement_default=0
- "Kanzi the Bonobo." NOVA. January 2007. (Dec. 10, 2010). http://www.pbs.org/wgbh/nova/bonobos/kanzi.html
- "Linking Research to Healthy Living." National Primate Research Centers, National Institutes of Health. (Dec. 8, 2010). http://www.sfbr.org/pdf/PrimateCenterBrochure.pdf
- McGrew, W. "Culture in nonhuman primates?" Annual Review of Anthropology. 27. 308-328. 1998.
- Morelle, R. "Chimps craft ultimate fishing rod." BBC News. March 4, 2009. (Dec. 8, 2010). http://news.bbc.co.uk/2/hi/7922120.stm
- Myowa-Yamakoshi, M., Tomonaga, M., Tanaka, M., and Matsuzawa, T. "Imitation in neonatal chimpanzees." Developmental Science. 7, 4. 437-442. (Dec. 9, 2010) http://onlinelibrary.wiley.com/doi/10.1111/j.1467-7687.2004.00364.x/abstract
- Nakamura, Michio. "'Gatherings' of social grooming among wild chimpanzees: implications for evolution of sociality." Journal of Human Evolution. 44, 1. 59-71. 2003.
- Nakatsukasa, M., Ogihara, N., Hamada, Y., Goto, Y., Yamada, M., Hirakawa, T., and Hirasaki, E. "Energetic costs of bipedal and quadrupedal walking in Japanese macaques." American Journal of Physical Anthropology. 124, 3. 248-256. 2004.
- National Human Genome Research Institute. "International genome team deciphers the genetic instructions for a complete animal." National Institutes of Health. Dec. 11, 1998. (Dec. 7, 2010). http://www.genome.gov/10000570
- "New genome comparison finds chimps, humans very similar at the DNA level." National Human Genome Research Institute, National Institutes of Health. Aug. 31, 2005. (Dec. 7, 2010). http://www.genome.gov/15515096
- Noonan, J., Coop, G., Kudaravalli, S., Smith, D., Krause, J., Alessi, J., Chen, F., Platt, D., Pääbo, S., Pritchard, J., and Rubin, E. "Sequencing and analysis of Neanderthal genomic DNA." Science. 314, 5802. 1113-1118. 2006. (Dec. 10, 2010) http://www.sciencemag.org/content/314/5802/1113.abstract#aff-4
- Palagi, E., Paoli, T., and Borgoognini Tarli, S. "Reconciliation and consolation in captive baboons (Pan paniscus)." American Journal of Primatology. 62, 1. 15-30. 2004. (Dec. 10, 2010) http://onlinelibrary.wiley.com/doi/10.1002/ajp.20000/abstract
- Premack, D. and Woodruff, G. "Does the chimpanzee have a theory of mind?" Behavioral and Brain Sciences. 1. 515-526. 1978. (Dec. 2, 2010) http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7131588
- "Primate Genomes." National Human Genome Research Institute, National Institutes of Health. Aug. 24, 2010. (Dec. 7, 2010). http://www.genome.gov/25521747
- Prost, J. H. "A definitional system for the classification of primate locomotion." American Anthropologist. 67, 5. 1198-1214. 1965. (Dec. 2, 2010) http://onlinelibrary.wiley.com/doi/10.1525/aa.1965.67.5.02a00060/pdf
- "Rh incompatibility." MedlinePlus. Nov. 15, 2010. (Dec. 7, 2010). http://www.nlm.nih.gov/medlineplus/ency/article/001600.htm
- Seyfarth, R., Cheney, D., and Marler, P. "Vervet monkey alarm calls: semantic communication in a free-ranging primate." Animal Behaviour. 28, 4. 1070-1094. (Dec. 9, 2010) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4K4PBD2-D&_user=10&_coverDate=11%2F30%2F1980&_rdoc=1&_fmt=high&_orig=browse&_origin=browse&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3c640a4e76d1954ef2070a713ec5850f
- "Stem Cells and Diseases." Stem Cell Information, National Institutes of Health. Nov. 23, 2010. (Dec. 7, 2010). http://stemcells.nih.gov/info/health.asp
- Thomson, J., Itskovitz-Eldor, J., Shapiro, S., Waknitz, M., Swiergiel, J., Marshall, V., and Jones, J. "Embryonic stem cell lines derived from human blastocysts." Science. 282, 5391. 1145-1147. (Dec. 7, 2010) http://www.sciencemag.org/content/282/5391/1145.full
- von Schaik, C., Deaner, R., and Merrill, M. "The conditions for tool use in primates: implications for the evolution of material culture." Journal of Human Evolution. 36. 719-741. 1999. (Dec. 8, 2010). http://www.gvsu.edu/cms3/assets/6D2549F6-ED41-142A-2D7251DEDEE796B4/deanerfiles/2vanSchaiketal1999PrimateMaterialCulture.pdf
- "What is a Genome?" National Center for Biotechnology Information. March 31, 2004. (Dec. 7, 2010). http://www.ncbi.nlm.nih.gov/About/primer/genetics_genome.html
- "World's Most Endangered Primates Revealed." International Union for Conservation of Nature. Feb. 18, 2010. (Dec. 9, 2010). http://www.iucn.org/?4753/Worlds-most-endangered-primates-revealed