MadSci Network: Evolution
Query:

Re: Cave men? WHA?! (read below)

Date: Tue Dec 21 12:04:08 2004
Posted By: Mark Spencer, Faculty, Dept. of Anthropology / Institute of Human Origins, Arizona State University
Area of science: Evolution
ID: 1103298501.Ev
Message:

Dear Tyler,

 	Human paleontologists, scientists who study the fossil record of human evolution, 
are very interested in what early humans ate and how they obtained it.  There are 
now many species of extinct humans known from fossilized remains dated to as 
early as 6-7 million years ago.  All of these are closely related to living people, but 
not all were our ancestors – there were many species that diverged from our 
ancestry, so the “tree” of human evolution looks a lot more like a “bush” these days.  
Not all of these species ate the same things, and they probably gathered various 
foods in many different ways.  For example, the “robust” australopithecines were 
specialized for eating some sort of tough food - perhaps seeds or root vegetables – 
and so they would acquire these foods in appropriate ways.  You ask about 
“capturing” food, so I assume you mean moving food, like animals.  Hunting is 
certainly something that some of us living people are good at, but when it came 
about as a behavior in the past has been a matter of some debate.  While it is easy 
to see if fossilized bones came from an animal that people butchered (and 
presumably ate), it is less easy to determine if the people hunted and killed the 
animal or if they simply scavenged food from other carnivores.

    	One suggestive observation that helps us to also answer your question 
regarding the roll of “instinct” is the fact that living chimpanzees hunt.  
Chimpanzees are not our ancestors, but they are our closest living relative, and we 
share a common ancestor with them that lived perhaps 7-8 million years ago – a 
species that split into two lineages that we and chimpanzees belong to.  Since both 
chimpanzees and living people can hunt animals, it is likely that our common 
ancestor could as well.  This may indicate that most early humans were capable of 
hunting, and perhaps did it occasionally (remember that hunting is only a small part 
of how even living people get their food). In chimpanzees, how to go about hunting 
is clearly something learned, not an instinct.  It happens only in some populations, 
and it happens in very different ways in different groups depending on what is 
being hunted and where it is found.  Chimpanzees are actually very sophisticated 
in their hunting, using calls and tactics to corner monkeys.  It is difficult to see this 
sort of behavior as an “instinct” since it is so variable among living chimpanzees.  In 
this regard, it is much like hunting behavior in living people – a learned behavior 
that gives access to certain valuable food resources. 

	I would encourage you to consider what is meant, exactly, by “instinct” and to learn 
more about what is known about the roll of instinct in shaping behavior in animals.  
For most mammals, at least, it is likely that many behaviors are learned, rather than 
being simply “hard-wired”, as the usual use of the term instinct implies.  If you have 
a pet dog or cat, you are undoubtedly familiar with this.  

Thanks for the great question!

Dr. Mark Spencer
Institute of Human Origins
Arizona State University








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