Primates
are our closest relatives in the animal kingdom.
How close?
According
to some unconventional scientific research, we may have more in common
with them than we thought.
About 250 miles east of Puerto Rico is an island in the Caribbean called Saint Kitts. Today it’s a popular tourist destination, but for more than 300 years it was best known as a producer of both sugarcane and rum, the liquor made from sugarcane. The first cane plantations were established in the 1640s by England and France, which both had settlements on the island. In those days, France also had colonies in Africa, and when French colonists from West Africa came to Saint Kitts, they often brought monkeys called vervets with them as pets. Many of these monkeys escaped into the wild, where they thrived in the tropical paradise, free from predators and disease. The vervet population exploded in the years that followed. There were plenty of mangoes for them to eat, and when mangoes weren’t in season, the vervets happily devoured the sugarcane, as an English visitor named Lady Andrews observed in 1774:
They are the torment of the planters, they destroy whole cane pieces in a few hours and come in troops from the mountains, whose trees afford them shelter… When pursued, they fly to the mountain and laugh at their pursuers, as they are as little ashamed of a defeat as a French general.
MONKEY SEE And just as vervets —like humans— acquired a taste for cane sugar, they also developed a taste for the rum produced from it. The monkeys probably got their first taste of alcohol by eating naturally fermenting cane stalks in the fields, then graduated to stealing rum whenever the opportunity presented itself. Islanders soon learned that an easy way to catch a vervet was to set out some rum in a bowl, then wait for one to come along and drink itself into insensibility.
As the years passed and Saint Kitts’s economy evolved from sugar and rum production to tourism, the vervets may have had an easier transition than the islanders did— at least as far as imbibing was concerned. Instead of heading out to the cane fields or into town in search of rum, the monkeys simply staked out the vacation resorts and stole drinks from tourists whenever their backs were turned. Some visitors found this annoying, of course, but for others, watching vervets steal drinks was —and still is— part of the experience of visiting Saint Kitts.
Vervets are one of few primate species (other than humans) that choose to drink alcohol. Though they’re covered in gray fur, have long tails, stand only two feet tall, and weigh less than 20 pounds, they share 90 percent of their DNA with humans. That has prompted scientists to study their drinking habits in the hopes of developing insights into the drinking behavior of humans.
MONKEY BARS
Ervin has conducted numerous studies over the years. Many have a similar structure. Vervet are given access to three kinds liquids:
1. Plain water
2. Water mixed with fruit juice or some other sweetener
3. Alcoholic beverages ranging in potency from 7.5 percent alcohol, about as strong as malt liquor, to 25 percent, which is stronger than wine but not as strong as the rum the vervet drink “in the wild.”
The vervet select what they want to drink and in what quantities. In some studies, the alcohol is available all the time; in others, it is only available at certain times of the day. Some times the vervet choose between alcohol served straight, diluted with water, or mixed with fruit juice. Whatever the case, the vervets decide for themselves what to drink.
GROUP DYNAMICS
“The parallels between the vervet’ behavior and human drinking is striking,” Ervin says. He divides vervet into four categories:
1. Teetotalers
Fifteen percent of vervet studied drink little or no alcohol at all. That’s a larger proportion than is found in those human societies where alcohol consumption is not forbidden for religious or other reasons.
The teetotalers preferred sweetened, non-alcoholic “soft drinks” over water. This distinguishes them from the vervets who do drink alcohol: all categories of those drinkers prefer water over soft drinks when they aren’t drinking alcohol.
2. Social Drinkers
Sixty-five percent of vervets drink small to moderate quantities of alcohol, and only when other monkeys are around.
Social drinkers prefer alcohol mixed with fruit juice or other sweeteners and rarely drink before noon.
Social drinkers are more likely to be female than male, and older males rather than younger males.
3. Abusive Binge Drinkers
Five percent of vervets will drink until they pass out in an alcoholic coma, “sometimes repeatedly within a 24-hour period,” if the alcohol isn’t allowed to run out or isn’t taken away. “They will stand at the alcohol bottle,” Ervin writes, “and will drink continuously, blocking access for all other monkeys.”
Binge drinkers prefer their alcohol straight or mixed with water rather than mixed with fruit juice or other sweeteners. They drink more in the morning than they do in the afternoon.
If access to alcohol is restricted to certain times of the day, the binge drinkers can consume an entire day’s worth of alcohol in as little as an hour. They will not drink water as long as alcohol is available.
Left to their own devices, abusive binge drinkers can drink themselves to death in amateur of months or even weeks.
Most abusive binge drinkers are young males.
Sixty-five percent of vervets drink small to moderate quantities of alcohol, and only when other monkeys are around.
Social drinkers prefer alcohol mixed with fruit juice or other sweeteners and rarely drink before noon.
Social drinkers are more likely to be female than male, and older males rather than younger males.
3. Abusive Binge Drinkers
Five percent of vervets will drink until they pass out in an alcoholic coma, “sometimes repeatedly within a 24-hour period,” if the alcohol isn’t allowed to run out or isn’t taken away. “They will stand at the alcohol bottle,” Ervin writes, “and will drink continuously, blocking access for all other monkeys.”
Binge drinkers prefer their alcohol straight or mixed with water rather than mixed with fruit juice or other sweeteners. They drink more in the morning than they do in the afternoon.
If access to alcohol is restricted to certain times of the day, the binge drinkers can consume an entire day’s worth of alcohol in as little as an hour. They will not drink water as long as alcohol is available.
Left to their own devices, abusive binge drinkers can drink themselves to death in amateur of months or even weeks.
Most abusive binge drinkers are young males.
4. Heavy Steady Drinkers
Fifteen percent of vervets drink as much as abusive binge drinkers but do so gradually, sipping it over time instead of drinking it all at once.
Heavy steady drinkers prefer their alcohol either straight or diluted with water, not sweetened with juice.
They tend to be dominant, sociable animals with strong leadership skills.
Males who drink heavily as adolescents, either as binge drinkers or heavy steady drinkers, are likely to continue drinking heavily into adulthood. Their off spring will, on average, drink twice as much as the offspring of social drinkers.
OTHER FINDINGS
Behavior
In vervet studies where access to alcohol is restricted to certain times of the day, in the hour before that time, the orkneys show “significant attention to the external environment” and “anxious attention to stimuli.” After the alcohol is made available, this heightened attentiveness and anxiety diminish considerably.
As wit humans, how vervets respond while under the influence of alcohol varies from one individual to the next. Some become more social; others are playful but keep to themselves and interact little with others in the group. Still other monkeys become withdrawn and remove themselves from the group, often retreating to a corner or sitting next to the alcohol bottle so that they can continue drinking. If approached by other vervets, they will either ignore the overture or respond aggressively.
Fifteen percent of vervets drink as much as abusive binge drinkers but do so gradually, sipping it over time instead of drinking it all at once.
Heavy steady drinkers prefer their alcohol either straight or diluted with water, not sweetened with juice.
They tend to be dominant, sociable animals with strong leadership skills.
Males who drink heavily as adolescents, either as binge drinkers or heavy steady drinkers, are likely to continue drinking heavily into adulthood. Their off spring will, on average, drink twice as much as the offspring of social drinkers.
OTHER FINDINGS
Behavior
In vervet studies where access to alcohol is restricted to certain times of the day, in the hour before that time, the orkneys show “significant attention to the external environment” and “anxious attention to stimuli.” After the alcohol is made available, this heightened attentiveness and anxiety diminish considerably.
As wit humans, how vervets respond while under the influence of alcohol varies from one individual to the next. Some become more social; others are playful but keep to themselves and interact little with others in the group. Still other monkeys become withdrawn and remove themselves from the group, often retreating to a corner or sitting next to the alcohol bottle so that they can continue drinking. If approached by other vervets, they will either ignore the overture or respond aggressively.
For
the group as a whole, when the monkeys are drinking, the total number
of social interactions increases… but the number of friendly or
“affiliative” behaviors such as grooming and huddling decreases. “The
increase was accounted for by fragmentary and inappropriate behaviors…
There were many aggressive overtures, including threats or slapping…
which were neither responded to nor followed up by the initiator,” Ervin
writes.
Play sessions between males who have been drinking are more likely to end in fights than play session between sober males.
Play sessions between males who have been drinking are more likely to end in fights than play session between sober males.
Miscellaneous
Adolescent vervet of both sexes, and adult females who have low social status in the group, Ervin writes, are not “over-represented among drinkers.”
Young vervet showed a greater preference for sweetened alcoholic drinks than did older vervets.
In one study, alcohol was available in unlimited quantities for three weeks and then suddenly taken away. The result: “abrupt withdrawal led to restlessness, cage pacing, voluminous consumption of [sweetened water], hyperirritability to sound or observer intrusion, tremulousness… and repeated approaches to the drinking bottle together with handling, rattling, and banging of the drinking bottle.
Adolescent vervet of both sexes, and adult females who have low social status in the group, Ervin writes, are not “over-represented among drinkers.”
Young vervet showed a greater preference for sweetened alcoholic drinks than did older vervets.
In one study, alcohol was available in unlimited quantities for three weeks and then suddenly taken away. The result: “abrupt withdrawal led to restlessness, cage pacing, voluminous consumption of [sweetened water], hyperirritability to sound or observer intrusion, tremulousness… and repeated approaches to the drinking bottle together with handling, rattling, and banging of the drinking bottle.
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