Institute of Medicine Questions Scientific Need for Chimpanzee Research

Pho­to: Chim­panzee being used for space research by the U.S. Air Force in the 1960s.

The Insti­tute of Med­i­cine con­vened an ad hoc com­mit­tee to answer two impor­tant ques­tions:

  • Is bio­med­ical research with chim­panzees “nec­es­sary for research dis­cov­er­ies and to deter­mine the safe­ty and effi­ca­cy of new pre­ven­tion or treat­ment strate­gies?”
  • Is behav­ioral research using chim­panzees “nec­es­sary for progress in under­stand­ing social, neu­ro­log­i­cal and behav­ioral fac­tors that influ­ence the devel­op­ment, pre­ven­tion, or treat­ment of dis­ease?”

The com­mit­tee was asked to con­sid­er only sci­en­tif­ic ques­tions, not ques­tions relat­ed to ethics or costs. The committee’s report con­clud­ed that most cur­rent use of chim­panzees for bio­med­ical research is unnec­es­sary and that the Nation­al Insti­tutes of Health should put strict lim­its on the use of chim­panzees as research sub­jects. The NIH has already announced a freeze on new grants for chim­panzee exper­i­men­ta­tion.

Some mem­bers of Con­gress want to out­law all exper­i­men­ta­tion on great apes, includ­ing chim­panzees (H.R. 1513: The Great Ape Pro­tec­tion and Cost Sav­ings Act).

Update: H.R. 1513 was not enact­ed.

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.

Why Gorillas, Why Not Chimpanzees?

Many peo­ple have asked me, why do you ask where goril­las get their pro­tein, when our bod­ies and our body chem­istry more close­ly resem­ble those of chim­panzees? My answer is that goril­las are much big­ger and more pow­er­ful than chim­panzees. Last night, I saw a muse­um exhib­it that com­pared a goril­la skull to a chim­panzee skull and a human skull. (They might have been mod­els. It was hard to tell.) The goril­la skull was huge! The chim­panzee skull was about the same size as a human skull.

The oth­er rea­son is that goril­las eat a much more strict­ly plant-based diet. Chim­panzees hunt once in a while, and they often eat their kill. Even so, they still eat a lot less meat than just about any human pop­u­la­tion. Nev­er­the­less, I was afraid that the fact they eat a lit­tle bit of meat now and then would mud­dy the waters.

My point is this. Most of the real­ly big and pow­er­ful land ani­mals got big and pow­er­ful by eat­ing plants. They don’t wor­ry about get­ting a pro­tein defi­cien­cy on a plant-based diet, and nei­ther should you.


(Image cour­tesy of Mahla­ti­ni Lux­u­ry Safari,

Where Do Gorillas Get Their Vitamin B12?

Termites: The Other, Other White Meat

Vit­a­min B12 is one of the two nutri­ents that are essen­tial for human beings but aren’t avail­able from a pure­ly plant-based diet. The oth­er is vit­a­min D, which isn’t tru­ly a vit­a­min but is a hor­mone that your body can make for itself if you get some bright sun­shine on your skin. Goril­las live in Africa, where there’s no short­age of sun­shine. The inter­est­ing ques­tion is where do they get their vit­a­min B12? Evi­dent­ly, they get it from the insects and oth­er creepy crawlies that they eat. Their favorites are termites—the oth­er, oth­er white meat.

As you can see, the goril­las just dis­man­tle the tree where the ter­mites are. That’s prob­a­bly why they don’t both­er using tools to fish for ter­mites, as chim­panzees do:

Except for vit­a­min D and vit­a­min B12, plants pro­vide all the essen­tial nutri­ents that peo­ple need. Plants con­tain min­er­als, such as cal­ci­um and iron, which they have absorbed from the soil. Plants con­tain all of the oth­er vit­a­mins and essen­tial amino acids, which they have made for their own pur­pos­es. Plants are also the orig­i­nal source of the essen­tial fat­ty acids. How­ev­er, plants don’t make vit­a­min B12, and nei­ther do ani­mals. All of the vit­a­min B12 in nature comes from bac­te­ria.

Some plant-eaters get their sup­ply of vit­a­min B12 from the bac­te­ria in their own diges­tive sys­tem, as long as they are eat­ing some­thing that con­tains the ele­ment cobalt. (Vit­a­min B12 con­tains cobalt). Cat­tle and sheep are par­tic­u­lar­ly good at get­ting vit­a­min B12 from their own gut bac­te­ria. They have a lot of bac­te­r­i­al fer­men­ta­tion going on in their stom­achs, so the vit­a­min B12 is made before the food pass­es through the part of the intes­tine where the vit­a­min B12 gets absorbed. Such ani­mals are called “foregut fer­menters.”

Oth­er species, includ­ing rab­bits and goril­las and human beings, are “hindgut fer­menters.” Their gut bac­te­ria make vit­a­min B12, but only after the food has passed through the part of the intes­tine where the vit­a­min B12 can get absorbed. Rab­bits solve this prob­lem by eat­ing some of their own drop­pings. Wild moun­tain goril­las some­times do the same thing, usu­al­ly dur­ing peri­ods of bad weath­er. Cap­tive goril­las do it a lot more often, pos­si­bly because they are bored.

On the oth­er hand, goril­las and human beings can eat foods that already con­tain ready-made vit­a­min B12. For goril­las, that means tasty, tasty ter­mites, which get vit­a­min B12 from their own gut bac­te­ria. Mod­ern human beings who don’t want to eat ter­mites, or any oth­er ani­mal prod­ucts, can get their vit­a­min B12 from a nice, clean, and very cheap sup­ple­ment. As long as their gas­troin­testi­nal sys­tem is healthy, peo­ple can even take their vit­a­min B12 by mouth. Vit­a­min B12 shots are use­ful for peo­ple who have trou­ble absorb­ing vit­a­min B12 from their food, because of gas­troin­testi­nal dis­ease.