Are We Getting Dummer

[Music]

about six years ago

in august of 2015 i took a business trip

to china

with my friend and business partner kobe

bryant pete delgrosso

and a few other colleagues we had a

number of meetings scheduled but the one

thing about travel in general

and travel to china specifically is

plans always

change a dinner with the ceo one evening

was cancelled last minute

so we found ourselves stuck eating

dinner at our hotel in shanghai

over dinner we caught up on business

family and then shifted to one of our

favorite topics

biology in nature we talked anecdotes

fun stories

oddities of nature concepts like how the

cheetah uses its tail to stabilize

itself as it leaps

how termites invented air conditioning

how ants created a version of the

internet

millions of years before humans did but

eventually

we moved on to my favorite topic the

human brain

given my background studying the brain

it was always fun to surprise people

with random anecdotes

it still amazes me how little people

know about our most important organ

the one that makes us conscious and

think and feel

the truth is though even experts don’t

know very much about the brain

as an example when i was in graduate

school we thought there were about a

hundred billion neurons in the human

brain

these are the fundamental building

blocks the computing units

and all you need to do is count the

little buggers but by my first book

the number had dropped we overcounted i

guess

and by my second book the number grew to

about 85 billion neurons

we missed a few so the most fundamental

thing about our brains

something we just have to count we don’t

really know

the thing that struck everyone most that

night though was when i casually

mentioned that regardless of the number

of neurons

our brains are actually shrinking mind

you

size doesn’t really matter we don’t have

the biggest brain in the animal kingdom

that honor goes to the sperm whale and

most brain scientists don’t think

absolute size matters at all

rather it’s the size of our brains

relative to our bodies

something known as encephalization but

even there

we don’t have the largest

encephalization the tree shrew of all

animals wins that award

but what does matter is how big our

brains are compared to our ancestors

and for most of hominin history our

brains were growing

both an absolute size and an

encephalization

and almost everyone agrees that the

growth and brain size over the past few

million years

has been responsible for our growing

intellect as our brains got bigger

so too did our mind’s abilities and

that’s where things stood

up until about 50 000 years ago when

things

seemed to have gotten a bit weird

somewhere around that time

our brains started to shrink and not

just by a small amount

i told the table that night to think of

our brain as roughly the size of an

american football

over the last 50 000 years we lost the

size of a baseball

in brain mass a baseball

my colleagues were in disbelief what

actually they almost seemed mad at me

for even suggesting it

but eventually someone asked the obvious

question

are we getting dumber i said we don’t

know

it’s possible that we’re losing

intelligence

but it’s also possible that something

else is happening you see brain size

tends to follow body size

which is why encephalization is so

important and it’s true

that our body size is also getting

smaller but that can only be part of the

story

both because our brains were previously

outgrowing body size

and on a relative basis our brains more

recently we’re getting smaller

as a percentage of body size our

encephalization levels are actually

shrinking too

there were plenty of theories to go

around and i shared a few of them

the most fun one was that some scholars

believe we’re getting domesticated

there’s actually strong evidence that

brings a domesticated animals

horses cows dogs cats shrink as a result

of domestication

they essentially lose their mammalian

brains

the area that focuses on being in the

wild but that was unlikely for us

because humans seemed to have lost brain

mass more broadly

and the decline has continued well past

our supposed domestication

so kobe did what i’ve seen him do so

many times before

he put his hand on his chin stroked his

beard

stared me down paid me a compliment and

challenged me to figure it out

so there i was in china with a challenge

i figured with the jet lag i wasn’t

going to sleep anyways so i said i would

see what i could come up with

that night i scoured the internet read

every journal article i could come up

with

and ultimately turned up empty-handed i

spent the next evening

doing much of the same and then went

back with my tail between my legs and

told kobe i couldn’t find anything but i

agreed to keep looking

weeks later same story

i researched every avenue i could find

many scholars

thought we were losing intelligence

others thought it was body size

some thought domestication as i’d said a

few thought it was structural but most

thought it was an anomaly just not

knowable

but at least i had my answer there was

no answer

so i told kobe who didn’t take it

particularly well

he said to me do you remember what i

told you

it was a fair question we were

jet-lagged and drinking really bad

whiskey that night

but i remembered and i told him so he

looked at me to be

to be fair he looked down at me because

we were standing

and said i didn’t say find out who has

the answer

i said find the answer if no one’s

figured this out

you should now i had some pretty

daunting phd advisors at brown and mit

but kobe was altogether different he

really didn’t take

no for an answer and i don’t know was

even worse

so i hemmed and hawed reminded him we

had a business to run

but reluctantly agreed to see what i

could come up with

for years my research became a running

joke

almost every time i saw him and it

didn’t matter who we were with

he would ask what have you got for me

jeff

everyone around us even my team figured

he was talking about business

we’re asking me to deliver bigger

returns or something truth is

neither of us cared to ask how the

business was doing our business was

doing amazing

there was no need to ask no kobe was

asking if i found an answer to the brain

science question

and each time i would say i’ve got

nothing

it wasn’t for lack of trying i ran down

every avenue

i started doing research in archaeology

paleontology physical anthropology

i reached out to neuroscientists

geneticists geochronologists

anthropologists i would have talked to

harrison ford if indiana jones was real

i started doing independent research

measuring fossils literally filling

skulls with all kinds of substances

to determine the size of the cranium and

then convert that into brain mass

estimates

i still have today what i believe is the

largest collection of brain size data

on the planet but i didn’t have

answers and then with the help of a

physiologist at johns hopkins medical

school

i found an answer the physiologist a guy

by the name of chris ruff

is a leading scholar of bone and body

mass changes in hominins

he wrote a seminal paper in nature

including data about how our body size

changes over time he even had some data

on brain size changes

chris was kind enough to give me updated

data on bone fragments and then formulas

to convert them to body mass

and when i compared the body mass

changes to brain size

sure enough body and brain size

correlated

even as the brain started to decline

as you can imagine i was pretty excited

i shot kobe a note hey we need to talk

we met at the nobu in newport beach

which had just opened

and with a half moon smile i fed him the

answer

no we’re not getting dumber it’s just

that our body sizes are shrinking

and the brain generally follows body

size just like all organs

that simple but kobe’s hand went back on

his chin

sat for a few minutes thinking as if

there was something to think about

i spent nights and weekends put off a

book we were writing together

i lost sleep but i found the answer

but when kobe finally opened his mouth

all he said was why

why why of course why how could i be so

stupid so what our brains are getting

smaller because our bodies are getting

smaller

why are our bodies and brains getting

smaller kobe my phd advisor

was right i didn’t answer the question

at all i just solved an interim step

so i responded the only way i knew how

more sake

and i drank and then i ubered myself

home that night

so for the next few years i continued to

do research

and continue to work on the problem but

i didn’t get very far

i had ideas but they were all just bad

ideas

and then early last year i lost my

friend

and everything changed it was

devastating

and it reminded me of the things that

mattered most in my life

so i decided to reprioritize

family and friends first the business

must

go on and i was determined to find an

answer

to why our brains are shrinking so i put

my hand on my chin

and i told myself you have one year

one year to find an answer no exceptions

over the course of the past year i asked

myself

every morning the same question kobe had

asked of me

what have you got for me in most

mornings i came up blank

but i persisted i continued to write

journal articles to make sure that my

thinking remained sound

and one day a criticism came back that

gave me an idea

a reviewer asked if i had controlled for

geography because different locations

had very different weather

and weather happens to affect body size

it turns out that people who live in

cold climates such as antarctica

or alaska tend to be stockier than those

who live in warmer regions

and this is true of the past as well

hominins evolved

to adapt to differences in geography

because of regional climate

the reason for this is thermodynamics

because our bodies produce

so much heat we need to regulate for

different environments

well the brain is the biggest energy

suck when it comes to all of our organs

our brains weigh roughly two percent of

our total body mass

but consume over 20 percent of our

energy

so it’s likely that our brains would

also need to adapt to thermodynamic

changes

if it were true for geographic

differences

i wondered if it could also be true for

climate change over time

i reached out to a few

paleoclimatologists and they provided me

with

millions of years of detailed sample

data you have to love scientists

business people would never share data

sure enough there was a strong

correlation between climate change

and both body and brain size during

cooling periods

our bodies and brains were significantly

bigger and during global warming events

our bodies and brain shrank there was

over a 10

percent difference in size across the

past 50 000 years

same pattern and of course during the

most recent period of global warming

we should then expect both body and

brain size to decline

and they did there was a slight twist

data is

never clean in science the last 1 000

years or so

has shown significant decreases in brain

size but body size has actually grown

so our encephalization shrunk but there

too we found an answer

it turns out we’re just getting fat

when you control for bmi or body mass

index the differences go away

so the answer is our brains are getting

smaller because of global warming

and they’re getting smaller relative to

the body because our bodies are putting

on

excess fat yet another reason to rid the

planet of climate change

and obesity there’s much more

to this story than science and finding

the answer to our shrinking brains

it’s also about how the best people push

us to go deeper

be better just as in the game kobe

pushed me further

made me dig deep on something in which i

thought there was no answer

even though it was in my own field he

never took no

or i don’t know for an answer our best

mentors do this for us

they push us inspire us

we give far too little credit to those

of us who teach

mentor coach we credit the individual

with success

whether it’s the scientists the ceo the

star athlete

the politician it’s worth asking if the

people behind the scenes

are in fact more valuable the people who

nudge

push motivate drive others that really

move this world forward

we should pay more credit to the

teachers in our lives and for my part

let this serve as a reminder of the good

that my friend did in this world

both for others and for me thank you