BY ROB DUNN ON JULY 23, 2012
PALEOLITHIC DIETS HAVE BECOME ALL THE RAGE, BUT ARE THEY GETTING OUR ANCESTRAL DIET ALL WRONG?
RIGHT NOW, ONE HALF OF ALL AMERICANS ARE ON A DIET. THE OTHER HALF JUST GAVE UP ON THEIR DIETS AND ARE ON A BINGE. COLLECTIVELY, WE ARE OVERWEIGHT, SICK AND STRUGGLING. OUR MODERN CHOICES ABOUT WHAT AND HOW MUCH TO EAT HAVE GONE TERRIBLY WRONG. THE TIME HAS COME TO RETURN TO A MORE SENSIBLE WAY OF EATING AND LIVING, BUT WHICH WAY? ONE GROUP OF SELF-HELP BOOKS SUGGESTS WE GIVE UP CARBOHYDRATES, ANOTHER THAT WE GIVE UP FATS, ANOTHER STILL THAT WE LAY OFF THE PROTEIN. OR MAYBE WE SHOULD JUST EAT THE WAY OUR ANCESTORS DID. A NEW CLASS OF VERY POPULAR SELF-HELP BOOKS RECOMMENDS A RETURN TO THE DIETS OF OUR ANCESTORS. PALEOLITHIC DIETS, CAVEMAN DIETS, PRIMAL DIETS AND THE LIKE, URGE US TO REMEMBER THE GOOD OLE DAYS. TAKEN TOO LITERALLY, SUCH DIETS ARE RIDICULOUS. AFTER ALL, LIKE ALL WILD SPECIES, SOMETIMES OUR ANCESTORS STARVED TO DEATH AND THE STARVING TO DEATH DIET, WELL, IT ENDS BADLY. THE PAST WAS NO PANACEA; EACH GENERATION WE MADE DUE WITH THE BODIES AND FOODS AVAILABLE, IMPERFECT BODIES AND IMPERFECT FOODS. BUT LET’S PRETEND, FOR THE SAKE OF ARGUMENT, THAT IT WOULD BE A GOOD IDEA TO EAT LIKE OUR ANCESTORS ATE. JUST WHAT DID THEY EAT?
HERE IS WHERE THE TROUBLE STARTS. COLLECTIVELY, ANTHROPOLOGISTS HAVE SPENT MANY A CAREER ATTEMPTING TO HONE IN ON THE DIETS OF OUR MOST RECENT ANCESTORS. TYPICALLY, THEY FOCUS ON OUR STONE AGE (AKA PALEOLITHIC) HUMAN ANCESTORS OR OUR EARLIER PRE-HUMAN, HOMINID ANCESTORS. EVEN IF WE JUST CONSIDER OUR STONE AGE ANCESTORS—THOSE FOLKS WHOSE STORIES SPAN THE TIME BETWEEN THE FIRST STONE TOOL AND THE FIRST AGRICULTURE—THE SIDES OF THE DEBATE ARE POLARIZED. IF YOU LISTEN TO ONE CAMP, OUR ANCESTORS GOT MOST OF THEIR NUTRITION FROM GATHERED FRUITS AND NUTS; SUCCESSFUL KILLS OF BIG MAMMALS MAY HAVE BEEN MORE OF A TREAT THAN AN EVERYDAY REALITY. A PAPER OUT JUST THIS MONTH SUGGESTS THAT EVEN NEANDERTHALS–OUR NORTH COUNTRY COUSINS AND MATES– MAY HAVE EATEN MUCH MORE PLANT MATERIAL THAN PREVIOUSLY SUSPECTED. MEANWHILE, MORE MACHO CAMPS OF ACADEMICS PAINT A PICTURE OF OUR ANCESTORS AS BIG, BAD, HUNTERS, WHO SUPPLEMENTED MEATY DIETS WITH THE OCCASIONAL BERRY “CHASER.” OTHERS SUGGEST WE SPENT MUCH OF OUR RECENT PAST SCAVENGING WHAT THE LIONS LEFT BEHIND, RUNNING IN TO SNAG A HALF-ROTTEN WILDEBEEST LEG WHEN THE FATES ALLOWED. IN OTHER WORDS, ATHOUGH “PALEOLITHIC” DIETS IN DIET BOOKS TEND TO BE VERY MEATY, REASONABLE MINDS DISAGREE AS TO WHETHER ANCIENT, PALEOLITHIC DIETS ACTUALLY WERE. FORTUNATELY, NEW RESEARCH SUGGESTS ANSWERS (YES, PLURAL) TO THE QUESTION OF WHAT OUR ANCESTORS ATE.ADVERTISEMENTADVERTISEMENT
THE RESOLUTIONS COME, IN PART, FROM CONSIDERING THE QUESTION OF OUR DIETS IN A BROADER EVOLUTIONARY CONTEXT. WHEN WE TALK ABOUT “PALEO” DIETS, WE ARBITRARILY TEND TO START WITH ONE SET OF ANCESTORS, OUR MOST RECENT ONES. I WANT TO EAT LIKE HOMO ERECTUS OR A NEANDERTHAL OR A STONE AGE HUMAN, MY NEIGHBORS TESTIFY. BUT WHY DO WE CHOOSE THESE PARTICULAR ANCESTORS AS STARTING POINTS? THEY DO SEEM TOUGH AND ADMIRABLE IN A REALLY STRONG FIVE O’ CLOCK SHADOW SORT OF WAY. BUT IF WE WANT TO RETURN TO THE DIET OUR GUTS AND BODIES “EVOLVED TO DEAL WITH” (A CONCEPT THAT WRONGLY ASSUMES OUR BODIES ARE FINE TUNED BY ENGINEERS RATHER THAN COBBLED TOGETHER BY NATURAL SELECTION), PERHAPS WE SHOULD ALSO BE LOOKING OUR EARLIER ANCESTORS. IN ADDITION TO UNDERSTANDING EARLY HUMANS AND OTHER HOMINIDS, WE NEED TO UNDERSTAND THE DIET OF OUR ANCESTORS DURING THE TIMES WHEN THE MAIN FEATURES OF OUR GUTS, AND THEIR MAGICAL ABILITIES TO TURN FOOD INTO LIFE, EVOLVED. THE CLOSEST (ALBEIT IMPERFECT) PROXIES FOR OUR ANCESTRAL GUTS ARE TO BE FOUND COILED INSIDE THE LIVING BODIES OF MONKEYS AND APES.
I SHOULD START BY EXPLAINING WHAT THE “GUT” IS AND DOES; I USE THE TERM TOO LOOSELY. WHAT I REALLY MEAN IS THE ALIMENTARY CANAL AND ALL OF ITS GURGLING BELLS AND WHISTLES. THIS CANAL IS THE MOST IMPORTANT AND LEAST LOVELY WATERWAY ON EARTH. IT TAKES YOU FROM THE MOUTH THROUGH THE BODY ALL THE WAY DOWN TO THE ANUS. BUT WHILE MOST CANALS TAKE THE SHORTEST COURSE BETWEEN TWO POINTS, THE ONE INSIDE YOU TAKES THE LONGEST. THE LONGER THE CANAL, THE MORE AREA OVER WHICH DIGESTION CAN OCCUR. FOOD ENTERS THE CANAL THROUGH THE MOUTH, WHERE IT IS CHEWED AND SLIMED WITH SALIVA. IT THEN HITS THE STOMACH, WHERE PROTEINS ARE DIGESTED (AND, I THINK, BACTERIA ARE FILTERED). NEXT, IT IS ON DOWN TO THE SMALL INTESTINE WHERE SIMPLE SUGARS ARE ABSORBED. IF YOU HAVE JUST EATEN A TWINKIE, THE PROCESS ESSENTIALLY ENDS THERE. EVERYTHING WORTH CONSUMING HAS BEEN ABSORBED. BUT IF YOU HAVE EATEN BROCCOLI, AN ARTICHOKE OR A FIG, THINGS ARE JUST BEGINNING. IT IS IN THE LARGE INTESTINE, WHERE HARDER TO BREAK DOWN CARBOHYDRATES (SUCH AS CELLULOSE, THE MOST COMMON PLANT COMPOUND ON EARTH) ARE TORN ASUNDER. THIS SYSTEM EVOLVED SO AS TO PROVIDE US WITH AS MANY CALORIES AS POSSIBLE (LONG TO OUR BENEFIT) AND, ALSO, AS MANY OF THE NECESSARY BUT HARD TO PRODUCE NUTRIENTS. THE ALIMENTARY CANAL IS, EVOLUTIONARILY SPEAKING, A MASTERWORK. IT MAKES ENERGY FROM THE FOOD WE ARE LUCKY ENOUGH TO FIND 1.
ALTHOUGH ALL GUTS ARE SUBLIME, JUST HOW THEY DO WHAT THEY DO VARIES AMONG SPECIES, MUCH AS DO THE LEAVES ON TREES OR BEAKS ON BIRDS. WHEN CONSIDERING EVOLUTION’S GREAT INNOVATIONS, DARWIN DALLIED AMONG THE BEAKS, BUT HE MIGHT JUST AS WELL HAVE FOCUSED ON THE GUT OR EVEN SIMPLY COLONS2. A BEAK CAN PICK SOMETHING UP, MAYBE CRUSH IT. BIG DEAL. A COLON CAN JUMP START THE PROCESS OF TURNING A BIT OF ROTTEN FRUIT OR LEAF INTO USABLE ENERGY AND ULTIMATELY LIFE. SCIENCE CAN REPLICATE A BEAK; IT IS STILL WORKING ON MAKING A GOOD REPLICA OF A COLON, MUCH LESS REPLICATING THE GREAT VARIETY OF COLONS AND GUTS MORE GENERALLY FOUND IN NATURE. CARNIVORES SUCH AS LIONS HAVE SMOOTH STOMACHS BIG ENOUGH TO HOLD A GOOD SIZED HUNK OF A SMALL ANTELOPE. IN THEM, THE MUSCLES OF PREY ARE RETURNED TO THE BITS OF PROTEIN OUT OF WHICH THEY ARE MADE. THE STOMACHS OF SOME HERBIVORES ON THE OTHER HAND ARE DENSE WITH HAIR-LIKE VILLI AND, MOVING AMONG THEM, THE BACTERIA THAT AID IN THE BREAKDOWN OF PLANT CELL WALLS AND THEIR CELLULOSE. THE STOMACH OF A COW IS A KIND OF GIANT FERMENTER IN WHICH BACTERIA PRODUCE HUGE QUANTITIES OF SPECIFIC FATTY ACIDS THE COW CAN EASILY USE OR STORE (YOU EAT SOME OF THOSE FATTY ACIDS WHEN YOU EAT A COW). IN OTHER SPECIES, THE STOMACH SCARCELY EXISTS AND FERMENTATION TAKES PLACE IN A GREATLY ENLARGED LARGE INTESTINE.
YET, FOR ALL OF THE VULGAR AND MAGNIFICENT ELABORATIONS ON THE THEME OF TUBES TO BE FOUND INSIDE ANIMALS, THE GUTS OF HUMANS ARE BORING (ALTHOUGH SEE FOOTNOTE 5). OUR GUTS ARE REMARKABLY SIMILAR TO THOSE OF CHIMPANZEES AND ORANGUTANS–GORILLAS ARE A BIT SPECIAL–WHICH ARE, IN TURN, NOT SO VERY DIFFERENT FROM THOSE OF MOST MONKEYS. IF YOU WERE TO SKETCH AND THEN CONSIDER THE GUTS OF DIFFERENT MONKEYS, APES AND HUMANS YOU WOULD STOP BEFORE YOU WERE FINISHED, UNABLE TO REMEMBER WHICH ONES YOU HAD DRAWN AND WHICH ONES YOU HAD NOT. THERE IS VARIATION. IN THE LEAF-EATING BLACK AND WHITE COLOBUS MONKEYS (AMONG WHICH MY WIFE AND I ONCE LIVED IN BOABENG-FIEMA, GHANA) THE STOMACH IS MODIFIED INTO A GIANT FERMENTATION FLASK, AS IF THE COLOBUS WERE KIN TO A COW. IN LEAF-EATING HOWLER MONKEYS THE LARGE INTESTINE HAS BECOME ENLARGED TO TAKE ON A SIMILARLY DISPROPORTIONATE ROLE, ALBEIT LATER ON IN DIGESTION. BUT IN MOST SPECIES THINGS ARE NOT SO COMPLEX. AN UNELABORATED STOMACH BREAKS DOWN PROTEIN, A SIMPLE SMALL INTESTINE ABSORBS SUGARS AND A LARGE (BUT NOT HUGE) LARGE INTESTINE FERMENTS WHATEVER PLANT MATERIAL IS LEFT OVER. OUR GUTS DO NOT SEEM TO BE SPECIALIZED HOMINID GUTS; THEY ARE, INSTEAD, RELATIVELY GENERALIZED MONKEY/APE GUTS. OUR GUTS ARE DISTINGUISHED PRIMARILY (ASIDE FROM OUR SLIGHTLY ENLARGED APPENDIX) BY WHAT THEY ARE MISSING RATHER THAN WHAT THEY UNIQUELY POSSESS. OUR LARGE INTESTINES ARE SHORTER THAN THOSE OF LIVING APES RELATIVE TO THE OVERALL SIZE OF OUR GUT (MORE LIKE 25% OF THE WHOLE, COMPARED TO 46% OF THE WHOLE IN CHIMPS). THIS SHORTNESS APPEARS TO MAKE US LESS ABLE TO OBTAIN NUTRIENTS FROM THE CELLULOSE IN PLANT MATERIAL THAN ARE OTHER PRIMATES THOUGH THE DATA ARE FAR FROM CLEAR-CUT. THE VARIATION IN THE SIZE AND DETAILS OF OUR LARGE INTESTINES RELATIVE TO THOSE OF APES OR GORILLAS HAVE NOT BEEN VERY WELL CONSIDERED. IN A 1925 STUDY THE SIZE OF COLONS WAS FOUND TO VARY FROM ONE COUNTRY TO THE NEXT WITH THE AVERAGE RUSSIAN APPARENTLY HAVING A COLON FIVE FEET LONGER THAN THE AVERAGE TURK. PRESUMABLY THE DIFFERENCES AMONG REGIONS IN COLON LENGTH ARE GENETICALLY BASED. IT ALSO SEEMS LIKELY THAT THE TRUE HUMAN COLONIC DIVERSITY HAS NOT YET BEEN CHARACTERIZED (THE ABOVE STUDY CONSIDERED ONLY EUROPE). BECAUSE OF THE DIFFERENCES IN OUR COLONS (AND ULTIMATELY THE NUMBER OF BACTERIA IN THEM) WE MUST ALSO VARY IN HOW EFFECTIVELY WE TURN CELLULOSE AND OTHER HARD TO BREAK DOWN PLANT MATERIAL INTO FATTY ACIDS. ONE MEASURE OF THE INEFFICIENCY OF OUR COLONS IS OUR FARTING, WHICH WE ALL KNOW VARIES PERSON TO PERSON. EACH STINKING FART IS FILLED WITH A MEASURE OF OUR VARIETY.3 ASIDE THEN FROM THE MODEST SIZE OF OUR COLON, OUR GUTS ARE STRIKINGLY, ELEGANTLY, OBVIOUSLY, ORDINARY.
ADULT FEMALE CHIMPANZEE (PAN TROGLODYTES) FEEDING ON A FIG (FICUS SANSIBARICA), A FRUIT THAT NEEDS TO BE HANDLE WITH CARE, LIKELY BECAUSE OF ITS HIGH CONCENTRATIONS OF CONDENSED TANNINS. KIBALE NATIONAL PARK, UGANDA. (PHOTO COURTESY OF ALAIN HOULE.)SO WHAT DO OTHER LIVING PRIMATES EAT, THE ONES WITH GUTS MOSTLY LIKE OURS, EAT? THE DIETS OF NEARLY ALL MONKEYS AND APES (EXCEPT THE LEAF-EATERS) ARE COMPOSED OF FRUITS, NUTS, LEAVES, INSECTS, AND SOMETIMES THE ODD SNACK OF A BIRD OR A LIZARD (SEE MORE ABOUT CHIMPANZEES). MOST PRIMATES HAVE THE CAPACITY FOR EATING SUGARY FRUIT, THE CAPACITY FOR EATING LEAVES AND THE CAPACITY FOR EATING MEAT. BUT MEAT IS A RARE TREAT, IF EATEN AT ALL. SURE, CHIMPANZEES SOMETIMES KILL AND DEVOUR A BABY MONKEY, BUT THE PROPORTION OF THE DIET OF THE AVERAGE CHIMPANZEE COMPOSED OF MEAT IS SMALL. AND CHIMPS EAT MORE MAMMAL MEAT THAN ANY OF THE OTHER APES OR ANY OF THE MONKEYS. THE MAJORITY OF THE FOOD CONSUMED BY PRIMATES TODAY–AND EVERY INDICATION IS FOR THE LAST THIRTY MILLION YEARS–IS VEGETABLE, NOT ANIMAL. PLANTS ARE WHAT OUR APEY AND EVEN EARLIER ANCESTORS ATE; THEY WERE OUR PALEO DIET FOR MOST OF THE LAST THIRTY MILLION YEARS DURING WHICH OUR BODIES, AND OUR GUTS IN PARTICULAR, WERE EVOLVING. IN OTHER WORDS, THERE IS VERY LITTLE EVIDENCE THAT OUR GUTS ARE TERRIBLY SPECIAL AND THE JOB OF A GENERALIST PRIMATE GUT IS PRIMARILY TO EAT PIECES OF PLANTS. WE HAVE SPECIAL IMMUNE SYSTEMS, SPECIAL BRAINS, EVEN SPECIAL HANDS, BUT OUR GUTS ARE ORDINARY AND FOR TENS OF MILLIONS OF YEARS THOSE ORDINARY GUTS HAVE TENDED TO BE FILLED WITH FRUIT, LEAVES, AND THE OCCASIONAL DELICACY OF A RAW HUMMINGBIRD4.