Why Do Chimpanzees Eat Meat?

Chim­panzees eat meat for two sim­ple rea­sons: they can catch it and they like it. Chim­panzees are par­tic­u­lar­ly like­ly to eat meat dur­ing the dry sea­son, when short­ages of the foods that nor­mal­ly make up the bulk of theirdi­et cause them to lose weight. Although the meat may be a use­ful source of calo­ries dur­ing the dry sea­son, wild chim­panzees don’t need to include meat or any oth­er ani­mal-based food in their diet to ful­fill their needs for pro­tein or any of the amino acids. In fact, plants pro­vide all of the nutri­ents that are known to be essen­tial for a chim­panzee, except for vit­a­min D (which they get from the abun­dant sun­shine in Africa) and vit­a­min B12 (which comes from bac­te­ria).

Many peo­ple think that I am sil­ly for ask­ing where goril­las get their pro­tein. They tell me that I should talk about chim­panzees instead. Often, they inform me that chim­panzees are far more sim­i­lar to human beings than goril­las are, as if I couldn’t tell that just by look­ing. These peo­ple are miss­ing my point: goril­las are the largest and most pow­er­ful liv­ing pri­mate and yet are the clos­est to fol­low­ing what human beings would con­sid­er a veg­an diet. Chim­panzees and human beings don’t need to eat meat to grow up big and strong because goril­las grow up to be far big­ger and stronger with­out it. Lawyers may rec­og­nize this as an a for­tiori argu­ment.

If a male goril­la, whose diges­tive sys­tem is prac­ti­cal­ly iden­ti­cal to a human being’s, can get enough pro­tein from veg­eta­bles to grow to weigh more than 400 pounds and be ten times as strong as a man, why shouldn’t I expect that a rel­a­tive­ly puny human Olympic weightlifter could also get enough pro­tein from a plant-based diet? My intent is to ridicule the Four Food Groups dog­ma that I was taught in sixth grade.

Goril­las don’t hunt or fish, and they don’t keep cows or chick­ens. As a result, they don’t eat meat or fish, dairy prod­ucts or eggs. The only ani­mal-source food they eat is “the oth­er, oth­er white meat”: ter­mites, slugs, and oth­er creepy-crawlies. These foods would make an insignif­i­cant con­tri­bu­tion to the goril­las’ pro­tein intake, which is already high because pro­tein accounts for a high per­cent­age of the calo­ries in leaves.

Bugs and slugs could be a use­ful source of vit­a­min B12, a micronu­tri­ent that is made by bac­te­ria in their intestines. Vit­a­min B12 is also pro­duced by bac­te­ria in a primate’s gas­troin­testi­nal tract. How­ev­er, the vit­a­min may be pro­duced so far along in the intesti­nal tract that it isn’t absorbed effi­cient­ly. No plants make vit­a­min B12, but goril­las and chim­panzees can prob­a­bly get enough vit­a­min B12 from the bac­te­ria in the bugs they eat and in the dirt that clings to their food. Plus, apes are not metic­u­lous about wash­ing their hands, if you get my drift. If you are wor­ried about get­ting enough vit­a­min B12, you don’t have to eat dirt or bugs. You can get it in a nice, clean tablet instead.

I don’t ask where chim­panzees get their pro­tein because chim­panzees do eat some meat. Chim­panzees prob­a­bly eat less meat than just about any human pop­u­la­tion oth­er than Bud­dhist monks. Nev­er­the­less, many peo­ple want to use chim­panzees’ meat con­sump­tion as an excuse for humans to eat meat.

The fact that chim­panzees’ meat con­sump­tion is large­ly sea­son­al goes far toward explain­ing why human beings have always eat­en meat. Chim­panzees are most like­ly to eat meat dur­ing the time of year when they are los­ing weight because their usu­al foods are in rel­a­tive­ly short sup­ply. Peo­ple think of meat as a source of pro­tein, but it’s main­ly a source of calo­ries, espe­cial­ly from fat. Meat is also a good source of sodi­um, which is in rel­a­tive­ly short sup­ply in the chim­panzees’ fruit and veg­etable diet.

The fact that chim­panzees eat the most meat dur­ing times of food short­ages sug­gests that their food choic­es fol­low a pat­tern that biol­o­gists call opti­mal for­ag­ing the­o­ry. Ani­mals try to get the most calo­ries for the least effort and with­out get­ting hurt. Opti­mal for­ag­ing the­o­ry explains why chim­panzees eat meat but goril­las don’t, and why chim­panzees eat more meat dur­ing times of food short­age.

Chim­panzees are main­ly fruit eaters, but they also eat a lot of veg­eta­bles. The prob­lem with fruit is that it’s sea­son­al. Worse yet, a fruit tree rep­re­sents a rich enough source of calo­ries that ani­mals will fight over it. When fruit is scarce, chim­panzees can use the skills they devel­oped in fight­ing over the fruit to engage in preda­to­ry behav­ior. Also, chim­panzees are small enough and fast enough that they are rea­son­ably good hunters.

Goril­las, on the oth­er hand, main­ly eat leaves. There are gen­er­al­ly plen­ty of leaves to go around, and a leafy plant is gen­er­al­ly so poor in calo­ries that it’s not worth fight­ing to pro­tect. To sub­sist on leaves, how­ev­er, you have to eat an enor­mous vol­ume of food. Since leaves are so low in calo­ries, leaf-eaters have to be good at con­serv­ing their ener­gy. That’s why goril­las have such a placid dis­po­si­tion. For a goril­la, hunt­ing is sim­ply not worth the effort. They are too big and slow to catch very much, and they’re large enough that they’d risk injury if they got too reck­less.

Chim­panzees use twigs to fish for ter­mites, and goril­las don’t. Some peo­ple think that this fact means that chim­panzees are smarter than goril­las. I don’t. If you are a juve­nile goril­la or a preg­nant or nurs­ing female goril­la, you don’t need to mess around with a lit­tle bit­ty twig to get a few ter­mites. All you have to do is wait for the sil­ver­back to knock over a rot­ting tree. Then all of you can eat as many ter­mites as you’d like.

Some peo­ple have argued that the bal­ance between ani­mal and plant foods in a hunter-gath­er­er society’s diet rep­re­sents the opti­mal bal­ance for human nutri­tion. I think that’s idi­ot­ic. Hunter-gath­er­er peo­ples (or should I say, gath­er­er-hunter peo­ples) tend to fol­low opti­mal for­ag­ing the­o­ry just like any oth­er oppor­tunis­tic feed­er. Their goal is to sur­vive in the short term, not to avoid breast or prostate can­cer in mid­dle or old age. The main threat to their short-term sur­vival is star­va­tion.

Meat rep­re­sents a con­cen­trat­ed source of calo­ries. The fact that a rel­a­tive­ly high per­cent­age of these calo­ries comes from pro­tein is actu­al­ly a dis­ad­van­tage. Hunt­ing peo­ples pre­fer the fat­ti­est foods. Peo­ple who end up hav­ing to sub­sist on extreme­ly low-fat meat, such as rab­bit, are prone to a prob­lem called fat-hunger or rab­bit star­va­tion. This prob­lem prob­a­bly results from a diet that has too much pro­tein and not enough car­bo­hy­drate or fat. On a low-carb diet and dur­ing star­va­tion, the body has to make its sug­ar sup­ply out of pro­tein. Per­haps the body can make only so much sug­ar out of pro­tein. As long as you are eat­ing enough fat to meet most of your ener­gy needs, your body can make enough sug­ar out of pro­tein to feed your brain. If you were eat­ing pro­tein but not enough fat or carbs, you could end up in seri­ous trou­ble. So you could end up in trou­ble from a diet that is too high in pro­tein. In con­trast, it is prac­ti­cal­ly impos­si­ble to avoid get­ting enough pro­tein, as long as you are eat­ing enough unre­fined plant foods to get enough calo­ries.

Famine is not a sig­nif­i­cant cause of death in the Unit­ed States. In fact, peo­ple in the Unit­ed States are far more like­ly to die of the dis­eases of afflu­ence, such as heart dis­ease and can­cers of the breast and prostate. Ani­mal-based foods and fat­ty processed foods are the main con­tribut­ing caus­es of the dis­eases of afflu­ence. The abil­i­ty to use ani­mals for food may have helped human beings sur­vive to the mod­ern era, espe­cial­ly in the Arc­tic, but ani­mal-based foods are a major cause of death and dis­abil­i­ty in the Unit­ed States today. Think about that the next time you hear some­one pro­mot­ing a “Paleo” diet.

9 thoughts on “Why Do Chimpanzees Eat Meat?”

  1. You are def­i­nite­ly my tribe. Paula Deen should be on death row, along with The Today Show cast which pro­motes her ani­mal, fat­ty foods even while crit­i­ciz­ing her for tak­ing mon­ey from the dia­betes indus­try — while she gives peo­ple dia­betes on pur­pose. Eat pigs and you look like a pig, aka Paula Deen and Al Roker.

  2. Unfor­tu­nate­ly, Paula Deen has put her­self on death row by giv­ing her­self dia­betes. Dia­betes is one of the major caus­es of death in the Unit­ed States, and it increas­es a person’s risk of dying of some of the oth­er major caus­es of death, such as heart dis­ease, can­cer, and stroke. If she uses antidi­a­betes drugs to con­trol her blood sug­ar tight­ly, her chance of dying could actu­al­ly increase.

    Per­son­al­ly, I’m too soft-heart­ed to give any­one the death penal­ty for any rea­son, but I would cer­tain­ly nev­er give it for hypocrisy. If all the hyp­ocrites were exe­cut­ed, who would be left to go to the funer­als? 😉

  3. Yes, there are veg­an body­builders and weight-lifters. See http://www.veganbodybuilders.com. They don’t look puny to me.

    The Food and Nutri­tion Board of the Nation­al Acad­e­my of Sci­ences con­clud­ed that there is no rea­son to believe that resis­tance train­ing increas­es dietary pro­tein require­ments for human adults.

    Olympic track star Carl Lewis, who had his best year of com­pe­ti­tion while eat­ing a total­ly veg­an diet, argues that most ath­letes suc­ceed despite their diets, not because of them. The fact that many weight-lifters eat raw eggs and so on is irrel­e­vant. If they get a boost from all that pro­tein-load­ing, it’s because the excess of high-qual­i­ty pro­tein is caus­ing their liv­er to secrete abnor­mal­ly large amounts of insulin-like growth fac­tor 1, which is also one of the most pow­er­ful known pro­mot­ers of can­cer growth.

    I am ful­ly aware that a goril­la-style diet would be imprac­ti­cal for human beings because it would take about 8 hours a day to eat enough leafy veg­eta­bles to get enough calo­ries. The prob­lem would be get­ting enough calo­ries, not get­ting enough pro­tein. If you read my Web site, you’ll find that I argue that the nor­mal diet for a human being is based heav­i­ly on unre­fined starch­es. How­ev­er, peo­ple who are try­ing to lose a lot of weight would ben­e­fit from “going ape” and eat­ing a diet more like a gorilla’s.

  4. I’m a veg­an and an athelete and can tes­ti­fy to the ade­quate pro­tien I get. Since switch­ing to veg­an I have made the same gains in the gym as when I eat meat, plus more plants means more vari­ety of carbs which fuels me for any endurance activ­i­ties. Weight lifters do need a lit­tle more pro­tein than the aver­age per­son. But what peo­ple fail to notice is that they also need more caror­ies as a whole. You may look at a body builders diet and say “wow, he eats 250g of pro­tein per day! that’s crazy.” but then if you look at body builder diets many eat more than 6000 calo­ries a day. Eat­ing 250g of pro­tien for 2000 calo­ries is a big feat, but have 6000 calo­ries makes it much eas­i­er. so now hav­ing 250g protein/6000 calo­ries is equiv­a­lent to only 83g pro­tein for an aver­age 2000 calo­rie diet. Many atheletes have the mind set of just eat­ing pro­tien and no calo­ries, which is ter­ri­ble.

    The only time peo­ple have pro­tein def­fi­cien­cies are when they are starved. The only pos­si­ble diet I can think of that is inad­e­quate would be a rice, sug­ar, butter/oil and alchohol deit. spinach has about 3g pro­tien per 20 calo­ries so if some­one just ate noth­ing but spinach they would have 300g pro­tein for just a 2000 calo­rie diet! now thats the pow­er of leaves!

  5. Thanks for com­ment­ing! Many peo­ple were con­cerned that the British food rationing sys­tem dur­ing World War I would lead to pro­tein defi­cien­cies. In response, a promi­nent British nutri­tion sci­en­tist wrote a book explain­ing that if you take care of the calo­ries, the pro­tein takes care of itself! The real cas­es of pure pro­tein defi­cien­cy are in the sort of sit­u­a­tions you men­tioned: peo­ple get­ting noth­ing but sug­ar intra­venous­ly or alco­holics. How­ev­er, rice does pro­vide enough pro­tein for human nutri­tion, includ­ing enough of all of the essen­tial amino acids. The beriberi that occurred in peo­ple who were eat­ing prac­ti­cal­ly noth­ing but unen­riched white rice result­ed from vit­a­min B1 defi­cien­cy, not pro­tein defi­cien­cy.

  6. Thanks for an intrigu­ing site, Lau­rie. I’m delight­ed that it is based on sci­ence and evi­dence. I trust that will safe­guard its slid­ing into some of the unre­lat­ed “woo” pseu­do­science that seems to infect many oth­er veg­an (among oth­er) sites.

    Your points are well tak­en. If I have any quib­ble it is the empha­sis on chimps as omni­vores as though that aspect of their diet were a giv­en. I wrote on that years ago, but I’m not aware that any of my sources have been dis­proven. As of that writ­ing it had been estab­lished that, where­as SOME chimp tribes, includ­ing, unfor­tu­nate­ly, the one Dr. Goodall stud­ied, do hunt mon­keys and eat them, not all tribes do so. Fur­ther­more, the hunt­ing of the mon­keys seems to have lit­tle to do with nutri­tion­al needs and is some­what sim­i­lar to a human sport, with the males doing the hunt­ing and estab­lish­ing hier­ar­chies there­by. The dead mon­key is usu­al­ly giv­en intact to a female in estrus, rather like, as I say in my paper, giv­ing a lady a posy when call­ing upon her. Why a female chimp would be recep­tive to such a mor­bid gift is puz­zling, but recent dis­cov­er­ies of female chimps car­ry­ing con­struc­tions of sticks as dolls may pro­vide a hint. The female will some­times car­ry the dead mon­key around for a long while before actu­al­ly tak­ing a bite. At an anthro­pol­o­gy con­ven­tion in Knoxville last year I learned that meat pass­es through the chimp diges­tive tract large­ly intact, sug­gest­ing it pro­vides the ani­mal with scant nutri­tion.

    My paper was titled “Of Men and Mon­keys, Memes and Meat,” and was online last time I checked; a search should turn it up. If not, I’ll pro­vide a link if request­ed.

  7. I do not con­sid­er chim­panzees to be omni­vores. A bio­log­i­cal omni­vore is an ani­mal that is adapt­ed struc­tural­ly and meta­bol­i­cal­ly to a mixed diet of ani­mal and plant foods. I con­sid­er chim­panzees to be her­bi­vores, main­ly fru­gi­vores. (Goril­las are main­ly foli­vores, which explains a lot of the phys­i­cal and behav­ioral dif­fer­ences between chim­panzees and goril­las.) How­ev­er, chim­panzees are, to some degree oppor­tunis­tic feed­ers.
    Chim­panzees occa­sion­al­ly do hunt, and they some­times eat their kill. How­ev­er, I have point­ed out that meat makes an insignif­i­cant con­tri­bu­tion to their total diet. They cer­tain­ly do not need it to meet their pro­tein require­ments. Chim­panzees prob­a­bly eat less ani­mal-source food than do any human society–except for The Veg­an Soci­ety, of course.
    I have heard reports that meat pass­es through a chimp large­ly undi­gest­ed, but I am inclined to doubt their verac­i­ty. There’s no rea­son to believe that chim­panzees would be unable to digest meat. In fact, this exper­i­ment sug­gests that they can: http://onlinelibrary.wiley.com/doi/10.1002/ajp.1350180105/abstract

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