Tomorrow's guest lecturer is Andrew Richards who just graduated in biology. He studied bottle-nosed dolphins in Australia. They have really large brains and he'll speak about primates and dolphins and intelligence and brainy things like that.

The Comparative Perspective

Nonhuman primate species as models

People have also used primate species as models of human behavior. This was originally the reason for anthropology departments to study primates. Early scientists, especially Washburn, wanted to know what primates could tell us about early humans. There have been a few ideas about how to choose the species you're going to get your information from- one is that you should look at primates who live in similar conditions to our ancestors- savannah baboons are a good example of this. Other people thought you should look at the most closely related species- chimps or some of the other great apes.

This has pretty much gone out of favor, however. There are several hundred species of primates and at least that many different human cultures-so it's too easy to find correlations and parallels. There's so much variability that you can back up pretty much any argument.

This is not to say that using primate models of behavior hasn't been useful. Particularly when the species and the question have both been chosen carefully, it has been helpful. Experiments with primates have been useful in psychology in studies on topics like motivations, drug addiction etc.

Example: Social development

This was done on rhesus monkeys to study social development in infants. It was found in countless studies that if an infant was deprived of social contact then it would grow up pretty screwed up- it would develop abnormal behaviors, and if you put it in with normal monkeys it would be overwhelmed by all the other monkeys. Then they thought, "Can these guys be resocialized by being put in with young normally raised babies who aren't threatening?" And it turned out that the pathological tendencies went away and they became normal monkeys. Then people did the same thing with kids who had been deprived at crucial parts of their lives and made them better.

Example: Mother-infant separation

This was also studied in rhesus macaques and pigtail macaques. They found that infants, when separated from their mothers, went though all these stages of separations- protest, despair etc. The saw the same thing with rhesus and pigtails, but in bonnet macaques, the infants don't go through all this psychological trauma. It's pretty clear why if you look at their social organization- there are a lot of allomothers in bonnet macaques and babies are often left by their moms in the wild and someone else will take care of it and bring it back to her later. So it's important to pick more than one species and to compare across species when you're doing this comparative approach for behavioral models.

Comparative analysis of human social organization

"The social life of monkeys does not lend itself to the formulation of any norm. Whether faced by male or female, the living or the dead, the young or the old, a relative or a stranger, the monkey's behavior is surprisingly changeable. Not only is the behavior of a single subset inconsistent, but there is no regular pattern to be discerned in collective behavior."

A more recent analysis
It isn't necessarily true that the main difference between humans and primates is based solely on our widespread use of symbols, but this is what people generally point to for what determines us from other primates. Using standard primatological approaches, however, how do humans look when compared to other primates? Some people here at UM looked at human society as a primate society. Of course there are a lot of different cultures. They focused mainly on traditional cultures which resemble what our ancestors probably lived like.

When you look across human cultures there's plenty of things that are different but there are some features that are pretty common;

• Usually, females disperse and males stay in their natal groups.
  
• Social organization is usually fission-fusion; We live in larger communities but don't all stay together at once. We break into smaller parties for daily life.
  
• We do, however, collect into stable groups to sleep together at night in a central place, while most fission-fusion primates sleep with whoever's there when night falls.
  
• Humans are mostly monogamous, but mildly polygynous.

These people also looked at what kind of relationships were maintained between individuals. They decided that these were crucial relationships in that species.

	Males Maintain Relationships with
Females Maintain Relationships with	non-kin only no other male male kin non-kin only mantled howler mountain gorilla Hamadryas baboon, red colobus, chimp, spider monkey no other female saddleback tamarin gibbon, titi monkey, orangutan female kin gelada baboon, capuchin black and white colobus, bushbaby human

They found it interesting that humans are the only species in which both sexes maintain social ties with kin, even after dispersal. This is probably important because it leads to extensive alliances between groups. In most primate species you can find stuff kind of like the human family, but they don't really have too many ties with other groups. But in humans, although we form families, we also make kinships ties through the males and the females. This is in spite of the fact that we don't have day-to-day contact with all these people. Scientists think this is only possible because we have this symbolic communication, and can speak of removed things.

We also are different because we (both sexes) cooperate with non-kin pretty often.
However, males cooperate with each other a lot in conflicts with other males. Females cooperate with each other a lot, but in non-conflict situations. In other primates, females help each other in conflicts, but in humans it's males extensively and females rarely.

This approach is purely descriptive- it's not to explain things or to understand them, but just to know what trends there are. So it's still left for someone else to generate hypotheses and tests and to see which behaviors are causes and which are effects and stuff like that in terms of human evolution.

Human ethology

Using principles from primatology

Kinship theory

This was traditionally a major focus of traditional socioanthropologists, but has fallen out of favor recently, but has always been popular with primatologists. People began to go back and apply it to humans. Mark Flynn did a study on a village in Trinidad and studied kinships. There were a number of stepfamilies where there were both full and step-children, and he wondered whether it affected the amount of investment from the father and found that it did indeed. Kids received less care when they weren't related to the father.

In this study, he also found that the % of interactions between kid and dad which involved conflict was about 3.5% for the genetic offspring, and 7% for the non genetic offspring. This wasn't child abuse but just conflict of some sort.

Another pair did a study on child abuse in Western society. They hypothesized that child abuse might be related to the amount of investment. They looked at child abuse rates in households with two genetic parents vs households with one genetic parent and one step-parent. Across all age groups, child abuse was much greater in families with one step-parent. Also, it was a lot higher in younger children.

Sexual selection theory

David Busse wrote a book and looked at human mate choice within a sexual selection framework. Remember that males are limited by access to females while females are limited by access to resources so males tend to be indiscriminate and females tend to be choosy. This guy looked at mate choice in humans and found there's a fair amount of choosiness in both species. Based on sexual selection theory, you'd expect males to be more interested in things that reflect a woman's ability to bear children, while women should be interested in the things which show that the male is able and willing to invest in the kids- so men looking for mates should pay a lot of attention to things that could indicate health, youth, fecundity etc, while women would be expected to look at status and wealth which indicate the male's ability to invest in offspring.

Another study has possible parallels which might have already occurred to us, but we might be interested to see results.

The question is, do males and females behave in the way you'd expect from sexual selection theory. Some researchers went to Florida State University and choose nine "reasonably attractive" undergrad helpers.They approached random members of opposite sex and said the following.

"I've been noticing you around campus and I find you very attractive. Will you..."

% Affirmative Answers

	Question	Males	Females
	"...go out tonight?"	50	56
	"...come over to my apartment?"	69	6
	"...go to bed with me?"	75	0

This certainly seems to indicate that humans behave like you'd expect them to as primates.

So these methods don't give us complete parallels, but they can give us information that we wouldn't come by using other methods.

At the turn of the century there were 20 species of bottle-nosed dolphins, twenty years ago there were three and now there is one. Nothing has gone away or gone extinct, it's just that perceptions and definitions have changed.

Measuring Brain Size

First we will talk about brain size, which is measurable, but is just a variable. It's thought to be correlated to intelligence but it's not a direct sign. However, no one has a real definition of how it connects.

How do we measure brain size? We have to have humans come out on top, or course, since we're so great. This means that we can't use absolute size because of elephants, sperm whales, etc. We also can't use a brain size to body size ratio because smaller animals like shrews have bigger ratios. So they use this other method in which they take the log of both numbers and look at who is above the line and who is below the line. In this way people have come up with an encephalization quotient. You look at how big the brain is and how big an average animal of that size is and plug in the numbers.

There's also another way to do it which is a little simpler. You take the body size in kg and the brain size in g and divide them. There are four different body size classes. In each class, there is a dolphin-like animal. In each class except the largest, there is also an ape. In each, at least one of the dolphins in the class has a bigger ratio than the ape (excepting the human who is far and away about the others).

So it's a costly organ, as he said before. Why has it evolved only in a few taxa? Basically just in dolphins and apes. A lot of speculation has gone on about human brain size as well; it has exploded in the last 2-5 million years. A lot of theories have come up to explain what caused the really fast development of brain size. They have all been very specific, for instance having to do with hand-eye coordination, tool use, or walking bipedally. However, it would be nice to have a general theory that explains large brain size in all taxa including dolphins who have no hands, no or very little tools, and don't walk bipedally.

Theories about Dolphin Brain Size

This may have given rise to the common myth that dolphins have x-ray vision and can see inside of things but they really can't. It's probably just that if something has air in it, they can tell that, and they can tell the difference between solid and hollow.

So a lot of their brain is probably devoted to echolocation and all this stuff. However, looking back at the chart of brain size to body size, we note that even though all of the dolphins echo-locate just fine, their brain size varies a lot- so the ones with the much larger brains must have a lot left over if you only need as much as the smaller-sized brains have for echo-location.

Theories about Primate Brain Size

There are two classes of general purpose hypotheses- The ecological model hypothesis (also known as the patchy resource hypothesis), and the social complexity modelling hypothesis.

Patchy Resource Hypothesis

Some species of primates have really patchy, ephemeral, somewhat unpredictable resources, specifically fruit. They need good cognitive skills to find their way around the forest, to find the fruit, to remember year to year which places had fruit, and to find their way around from fruit tree to fruit tree efficiently. Folivores don't have to look so hard for their food. It is well known that using a variety of measuring systems, folivores have less brain capacity than frugivores. Howlers and spider monkeys, for instance, live in the same habitat and are roughly the same size, but one is folivorous and the other is frugivorous, and they have different brain sizes.

One criticism- people like to talk about encephalization (increase of brain size with body size) but it's well known that animals who eat cellulose (grass, leaves, sticks, bark) have a tough time digesting this and they have long guts to digest it. So folivores may be somaticized because of the need for bigger guts- so for a given brain size, folivores might have bigger bodies because they need the space. In other words, maybe it's not that the folivores have smaller brain for their body size, but just that they have larger bodies for their brain size. Anyone who deals with this hypothesis has to take this into account.

Another word of warning about any of these hypotheses- there's a difference between the origin and the maintenance of a trait. The reasons for which cognitive skills and large brains evolved may be different from the things they're being used for today. For example, our brains probably didn't evolve to do calculus, but we use them for that anyway. So it is possible that a species that evolved a large brain to find fruit now has a lot of social skills that they use the brain for, or vice versa. It might have evolved to get through a complex social life but now they use to it find fruit better.

Social modeling hypothesis

If you live in a complex society, then you're going to have a brain that can grasp who's who and who's with you and who's against you and what they're going to do tomorrow and whether their friends are there. Just to make your way through this complex society takes a large brain.

This theory is interesting because both chimps and bottle-nosed dolphins live in complex social systems. In chimps, females disperse while males live with related males and form alliances with each other against individuals in their own groups and against neighboring communities. A group of males from one community often fights males from another community. Bottle-nosed dolphins have a remarkably similar social system.

Dolphin Social System

Dolphins have huge testes for their body size, which is indicative of sperm competition, which indicates that the females mate with several males. Researchers have not seen mating too much, but they've seen females consorting with up to thirteen different males in the season during which they conceived. Females first give birth at about 12 years old. They have a long period of infancy; a kid might still be suckling at like 5 or 6 years old. Mothers invest heavily in the kids, who are socialized during infancy and juvenilehood.

Dolphins have a fission-fusion social system; they live in a larger community but break into smaller parties for day-to-day life, just like chimps. However, they don't just have random associations; females have one or more other females that they're often found with but not always, while males have one of two other males that they are almost always found with. Female associations might be several females travelling together. Male alliances, however, are usually just one or two other guys. The male alliances cooperate to coerce females in estrous to stay with them.

The males work together to herd the female. Often they are seen directing aggression at her to get her to stay with them; biting, hitting, or threatening her. Sometimes she stays with them for weeks, but it doesn't always work, 'cause during the breeding season, females hang out with a few different alliances. The female often tries to escape, which is how they know it's coercion. Sometimes the males give chase, and sometimes they let her go.

There are two levels of male alliances- pairs/triplets often join together with other pairs/triplets to steal females from other alliances. They'll charge into other alliances and grab the female. Sometimes she cooperates with them and sometimes she doesn't. Females also form alliances with each other, and he thinks that maybe they're helping each other to get away from the males 'cause they usually form these coalitions when one is in estrous.

How Well the Social Modelling Hypothesis Explains Large Brain Sizes

There's also the anecdote about two vervets having a fight. Right in the middle of the fracas, one yelled "leopard!" and the fight broke up.

A warning: It's very easy for us to attribute motivation, personality, and intentionality to things. We name our hurricanes, for goodness sakes! We have to be careful we're not doing this by accident when we're looking at smart animals.

An overview of the course

Then we looked at some ecological aspects of behavior- how they feed themselves, how they space them selves out, what kind of groups they live in, and who they mate with. Building on the whole issue of mating and its central role in evolution, we developed the theory of sexual selection, in which females are choosy and males are more indiscriminate.

Then we went on to look at social behaviors, and developed theories on why primates live in groups based on increasing the ability to get food and to avoid predators.

Having established that all primates live in groups, we went inside the groups and looked at how their groups are structured. We found that social behavior within groups is structured by social relations. It also involves various types of altruistic and cooperative behaviors. Altruistic acts pose something of a challenge to natural selection theory, which would predict selfish behavior, and we looked at considerations of kinship and degrees of relatedness to see how these things might still benefit the donor. Some specific examples we looked at were cooperative polyandry and allomothering. We explained these phenomena using the principle of inclusive fitness.

Then we looked at social relationships between different species, between females, and between males and females. In particular, we took a closer look at the unusual phenomenon of female dominance. We also looked at interactions between adults and infants, including infanticide by males. We concluded our journey through the primate world with a short discussion of what they say to each other and by looking at the question of what makes them so darn smart.

He has taken occasional opportunities and recently took a whole lecture to look at how primates are similar and different to each other but also similar to and different from us.

"It would be no less wrong than absurd to deny the existence of this chasm, but it is at least equally wrong and absurd to exaggerate its magnitude, and, resting on the admitted fact of its existence, refuse to inquire whether it is wide or narrow." -1863