How the Nature/Nurture Debate is Changing

this is my box of human nature it contains everything in it that's in your nature what does that mean well in short if it's in your nature it's unchangeable it's undeniable it's part of your very constitution and it's in a box because it's impervious to everything outside of it locked in a cage unadaptable the question is what do you think is in the box do you think the box is full empty somewhere in between on the other hand outside of the box we have all of this the environment all that stuff around you that's ever been around you that has an effect on you how you're formed how you develop who you are as a person does any of this get inside the box maybe the box is empty a blank slate does the philosopher john locke put it filled up as you grow up as you develop seriously what do you think might be in here we're going to skim over some complicated sounding things dna genetics epigenetics methylation phenotypes stress twin studies stephen pinker and early intervention programs but i want to avoid being technical as much as possible because most crucially most simply this box is about a fundamentally philosophical idea freedom [Music] debates about nature nurture inform almost every area of human life from biology and botany to economics literature and history to simplify thinkers on the nature side have in varying ways argued that at least parts of your body and mind are behind an impenetrable skin cannot be gotten to by upbringing education politics or culture they're often referred to as nativists they believe we have an innate human nature of course it's undeniable that people grow change adapt interact with the world but nativists believe that this change at least in some parts emerges from the box imagine a one-way street you might have an innate eye color or a creativity that comes out of your dna one way nothing gets in to it to take one example the english philosopher thomas hobbs argued that we are naturally competitive we sought glory we're prone to violence these things come out of us they have an effect on others but no culture politics education upbringing or environmental change could change that fundamental universal timeless fact on the other hand we have empiricists they roughly speaking believe in a two-way street instead of a one-way street another english philosopher john locke for example thought that the mind was a tabular rosa a blank slate and all humans were shaped in different ways by their experiences what they see hear touch what they're taught how they're raised experience comes in okay let's return to those nativists the ones who believe that we have a nature what is it that they actually believe is behind the barrier in the box well depending on who you ask it can be anything from iq a capacity for violence economic self-interestedness a propensity for addiction the likelihood of a certain disease at a certain age the list goes on there are two things i want to think about here first what does the evidence say and second what are the consequences of that evidence today for philosophy and politics what does it mean for human society if either nature or nurture are true the central point that's been made across the history of this debate is this if people have a nature if they're trapped in the box then it's no good doing any intervening to try and improve things intervention here is the key word what parts of us are malleable and who or what is shaping those parts who or what is intervening nurturing upon our lives will return to this question at the end but first the idea that we have a nature has been approached in countless ways philosophically psychologically theologically but the most persuasive throughout the 19th and 20th centuries the best place to start is biology the study of dna and our genes okay bear with me while we get technical for just a second to get to the foundation of nature nurture we have to talk about dna all of life is about replication you came as most species did from a single cell a cell that contains everything that's in your nature everything that's in that box the cell duplicates and divides into two which then divide into four and to eight and 16 and 32 and so on until in a human they reach 50 trillion each of those cells contains dna in the nucleus in the center which is made up of a long double helix of chemicals called base pairs humans have three billion base pairs and they are 99 identical for all of us the order of those base pairs which are made up of only four molecules a g t or c determine everything from eye color to toenails to neurons the order of the base pairs in the dna tells the cell what to do and how to replicate itself and when a cell replicates the dna helix unravels and tells the cells which ingredients it needs to make two new strands genes and the dna that make them guide everything in life they tell the cell which proteins to make which are the building blocks of all life proteins make up the structure of the body used to transport blood used as antibodies as a defense they come in all shapes and sizes and there could be up to 400 000 proteins in the human body and the code for how to make them comes from the dna strands in each and every cell so if anything is in the nature box dna is it's at the bottom of that one-way street the absolute inside dna replicates itself passes it on into the next box it creates it contains the ingredients the blueprint the code to make someone tooled or intelligent or a self-interested hobsyan bruler or autistic maybe or quick wit it and no amount of environmental stuff outside can change it because it stays the same in every cell from when you're born to when you pass down your genes to the next generation but is this really true remember all of life is about the duplication of cells and all of cells contain the same dna your human nature and your dna is your dna unchangeable by the environment around it but when this was discovered in the 19th century some people began to wonder if dna makes everything but always the same in each cell of the creature how does when it replicates it begin to know when to make a head a nose a liver a neuron a hair a nail a blood cell when the first cell you came from divided into two did one of those cells contain your legs and your feet and the top contain your neck and head and brain one scientist hans dreisk even decided to separate the cells of sea urchin embryos thinking they'd grow into two separate deformed sea urchins a top and a bottom but to his surprise they grew into two normal healthy urchins in other words when our cells divide there must be some mechanism for telling the cells how to divide something to tell the dna what to do so it cannot be a one-way street something some message has to go the other way has to get to the box to signal to it what to do where does this come from the answer of course the environment dna must be nurtured in some way nobel laureate christian newslane volhard writes that the cell receives signals and information from the environment including the neighboring cells this information is transmitted to the genes in this manner the fate of a cell is dependent on both the cytoplasm and external influences so what the dna does depends on how it interacts with other molecules the proteins and cells it encounters that is everything around it it receives signals in some way from the environment it cannot be a one-way street but how only in the last few decades has a revolutionary answer to this question been discovered one that's having a huge impact on almost every field from biology to philosophy epigenetics [Music] okay back to that one-way street genetic determinism is the idea that your characteristics and traits come out of the box that they are nature and they come out in the same way irregardless of any environmental interaction with them they come out of your dna and make you epigenetics meaning on or above genetics is the discovery that whatever's in the box can be switched on and off and even more than that can act like a dimmer switch producing more or less of some quality to know what to do how to act dna requires signals from the environment it needs to know which of the millions of combinations to execute and express it simply cannot be unresponsive to environmental signals dna contains so much data it boggles the mind if unwound it would be around 2 meters long in each of those 50 trillion cells but certain molecules from the environment called histones and methyl groups can wind themselves around the dna bunch it up so that a particular part of the dna cannot express itself the information is silenced this is called methylation another group of chemicals acetals open the dna so that it can express itself again these processes are the ones that are right at the foundation of nature nurture and show us that that duality of nature or nurture is nonsensical what we in some way have and even this isn't accurate is nature and nurture interacting in a dance dna has what biologists call regulatory sites that different molecules are able to bind to changing the function of the dna telling it what to do this discovery has had some groundbreaking implications for so many areas memory cancer depression obesity autism addiction aging exercise nutrition toxins we'll look at a few of them and then we'll return to think a little bit more about some philosophy and think of the implications of what we've learned randy gertle and michael skinner writes that the word environment means vastly different things to different people for sociologists and psychologists it conjures up visions of social group interactions family dynamics and maternal nurturing nutritionists might envision food pyramids and dietary supplements whereas toxicologists think of water soil and air pollutants but scientists now have evidence that these vastly different environments are all able to alter gene expression and change phenotype that is the characteristic the trait like eye color in part by impinging on and modifying the epig name i want to ask this what are the clearest places this process happens where does the environment affect us in ways we have direct evidence for are those places limiting or expanding our freedom and how can we think about that more simply and more philosophically how can we think about the consequences one toxins and pollutants they've been shown to have an effect on cognitive functioning of children as do mercury in some plastics and pesticides pollution in the form of fossil fuel combustion has been shown to be associated with poorer test results in the kids frequencies of refuse collection access to toilets and cleanliness of water have all been shown to be associated with cognitive performance in many low-income countries and of course all of these disproportionately affect poorer neighborhoods two noise aircraft traffic crowded living conditions can all lead to poorer reading skills higher blood pressure and an increase in stress hormones poorer parents have less time to stimulate infants which has negative outcomes later in life a lack of stimulating materials books toys etc has the same results smaller classrooms on the other hand have a positive effect 3. nutrition it's been found that a whole range of dietary habits leave epigenetic marks stress or famine even when you're in the womb lead to outcomes like obesity and stress for decades into the future four five and six stress anxiety and depression or mental health disorders more broadly okay let's slow down i think stress is important it shows a lot about this topic studies have shown that rats who are licked and groomed by their mothers in the first 10 days of their lives respond better to stressful events later in life rats from low licking and grooming mothers are more likely to become startled and act fearfully throughout their lives and researchers found that the dna had been methylated to stop a stress-reducing hormone from being produced neuroscientist david moore writes that this conclusion is supported by a study of rat pups whose mothers were so stressed out that they treated their newborns abusively by frequently stepping on them dropping them dragging them or handling them roughly as a result of this mild treatment the offspring grew up to have altered patterns of methylation in their brains and studies on mice and monkeys show similar epigenetic changes throughout their lives the breadth of these studies has important philosophical and political consequences when it comes to stress our bodies are almost identical to rats but furthermore suicide victims have also been found to have high levels of genetic methylation as have victims of abuse and individuals whose mothers had depression while they were pregnant the thing with the thing with methylation is that it's hard it's hard to get off it's sticky so early childhood experiences can literally get under your skin and really affect how your dna operates for the rest of your life another study found a relationship between poverty in the first five years you've lived and epigenetic changes 20 to 35 years later it makes complete sense that animals and humans from more stressful early infant environments display high stress responses later in life because the environment you're born into is a good predictor of what the rest of your life might look like you might need your body to fight or flight more have higher stress responses in areas with more predators or more loan sharks poverty becomes biology but you might be saying of course there are still things in the box we have the dna you couldn't epigenetically adapt the dna to produce wings and some people are surely naturally better at certain things and not as good at others the dna is surely still the dna well to think about this we need to look at twins the identical twins have and come from the same box if they're raised in different environments and the same stuff comes out well the box is unchanged we've found nature whatever it is the largest study of twins started in 1994 and looked at over ten thousand pairs of twins from the uk the us and the netherlands they looked at twins who have been raised together raised together up to a certain age and raised apart and look for similarities and differences between them if they've been raised apart all their lives but display identical traits than it must be in the dna regardless of the environment to summarize the results briefly researchers have estimated that around half of these twins traits could be attributed to their genes and the other half to their environment so around half and half it's been found in another recent study that young identical twins have similar epigenetic markings but as they get older they diverge in other words as their environment and experience changed them intelligence is also found to be increasingly heritable as twins get older that is as twins catch up with each other regardless of their environment how they've been raised where they went to school where they live some researchers have put the number as high as two-thirds nature and just a third nurture but are we really seeing nature in these studies first in one recent matter study that's a study of studies it's been found that in most of them the term raised apart was used very loosely many of the twins were actually raised together and many knew each other one study reviewed 121 cases that claimed to be raised apart only three had actually been separated shortly after birth and only just been reunited most had actually had an average of 10 years together at some point many of them were separated between the ages of 8 and 11 and most almost all in fact shared the same culture the same socio-economic background or knew each other as adults and on top of this of course they shared the same environmental signals in the womb and the same conditions in the first weeks of their lives look at this quote from epidemiologist david barker about plasticity in development he says there are good reasons why it may be advantageous in evolutionary terms for the body to remain plastic during development it enables the production of phenotypes that are better matched to their environment than would be possible if the same phenotype was produced in all environments plasticity during intrauterine life enables animals and humans to receive a weather forecast from their mothers that prepares them for the type of world in which they have to live if the mother is poorly nourished she signals to her unborn baby that the environment it is about to enter is likely to be harsh the baby responds to these signals by adaptions such as reduced body size and altered metabolism which help it to survive a shortage of food after birth [Music] okay let's try and bring this together in some way there are things in the box propensities maybe but they're expressed in a wide variety of ways epigenetically depending on how they interact with the rest of the environment the way our nature is expressed is dependent on a wide range of phenomena like we've seen toxins pollutants stress education culture politics prolonged experiences levels of threat in womb development the list is endless and we're only really just starting to see how far it goes so does that mean we're more blank slates or do these propensities mean we have a type of human nature how can we make sense of this so we have to ask do separated twins really escape this environmental effect stephen pinker's influential book the blank slate has a handy list of what he and anthropologist donald brown describe as human universals meaning in our nature impervious to everything outside of it the environment pinker handily tries to list all of them you can see them through the link i've put in the description below have a look some of them like tools fear fire and cultural relativity just to name a few are almost laughable or at the very least simplified or shallow fire for example it's not human nature it's not in our dna in our genes it's environmental it's an interaction and also i could conceivably live my entire life without it and we have innovations that have superseded it in some way and that's just one but take fear okay we all i think with a few exceptions have experienced fear is it nature or nurture then i'd say we have something like the raw ingredients for fear or a propensity for fear in the box but the way those ingredients come together and are expressed and interact with the environment are impossible to understand without looking at the outside world looking at culture and society and philosophy and change i think you can still despite things like a propensity for fear being in the box make a strong case for something like blank slatism there is no sense in which an idea or feeling of fear is imprinted on the mind or body for that matter in a universally genetically determined specific way before you were born you have the biochemical propensity the ingredients for it in your dna the dna is then epigenetically expressed in a variety of ways and depending on your environment which includes the womb and the parents environment remember before it even gets to the slate of the mind the blank slate it's then mixed with other cultural social and environmental factors that we absorb from experience that code or script the biology chemistry and idea of fear in many ways which may or may not depending on the period and the culture be expressed in particular ways for a particular period of time with certain triggers of course what many of us are interested in when we're talking about nature nurture is not that we have fears hormones legs need food have a culture those human universals but how those supposed universals are expressed in the environment by the environment how our dna unfolds collides synthesizes with the rest of the world and that genetic determinism the idea that nothing gets to the box and everything comes out justifies one political cultural and social position in particular individualistic non-intervention but because people are what their genetic inheritance is intervention is an intrusive waste of time money and resources so if our genes are now conclusively affected by the environment what does this mean philosophically culturally politically well we are intervened upon by our environment to other people in a way that's outside of our control when we're young the obvious question here is where does this happen in a detrimental way and where does it happen in a useful way you could go in many directions with this but here are a few consequences i think we can take from what we've looked at first responsibility and blame if we're affected in our genes by pollution upbringing economic development stimulation of many kinds then we have to acknowledge that there are more people responsible for their genetic expression in one person than that individual themselves who then is responsible the parents the wider community the polluter the nation these are wider questions about justice second liberty the political philosopher assaiya berlin talked about negative liberty the freedom from interference and positive liberty the freedom to do something science can help us think about both to grow in an environment free from pollution is one thing but to live in a stimulating environment to have access to books to good education welfare creates the freedom to do more later in life i think thinking about epigenetics allows us to think about those freedoms from things and freedom to develop in the fullest possible way that's a social responsibility because the individual is not responsible for how he's developing at that young age third we might think about intervention who's best suited at what times and where one of the most interesting conclusions from recent epigenetic studies is that much of this happens and happens to us in the first few years of life if not in development in the womb so before we end i think it's important to have a quick look at where i think many of these studies lead early intervention i think one of the main takeaways from all of this is how much the first few years of a child's life including the nine months of pregnancy affect them for the rest of their lives we usually think of education as the primary mode of improving a child's environment but that's not enough a uk government report found that funding should be shifted from later to earlier interventions and the children's charity the wave trust argues that governments should focus on preventing adverse childhood experiences like abuse neglect and mental illness etc and we already have some programs like this short start in the us and head start in the uk but i think we're only just beginning to work out how to best utilize them the first head of head start naomi eisenstadt wrote on the london school of economics blog that the substantial success of the surestart scheme has been that the argument about the role government should play between birth and school is now one we no longer need to deliver more evidence that the preschool years are vital to children's development and the provision of services for young children and families is critically important the acceptance that there should be provision for such services and that government has a role in regulating and at least partly funding this is now firmly in place there are also programs like the nurse family partnership in the uk that assigns nurses to low-income families for frequent visits but we also need to recognize that this isn't enough a handful of visits and limited funding cannot make up for a history of generational poverty we should treat having children like the most highly skilled job you can possibly do because it is and it has the most consequences for society we should offer extensive education and courses to pregnant couples and ensure the home environment is as good as it possibly can be we should extend parental leave and reorganize child care around the discovery that the first few years of a child's life are crucial this is before we even get to the moral and ethical case just a good return on investment it used to be thought that genetics were passed down like a blueprint a precise guide to engineer the body a code a script a recipe book maybe but genetics are more like a script that can be read differently depending on the context as nasa kerry has argued different interpretations of romeo and juliet say change over time in movies stage song retellings in literature but i think we can go even further than that it turns out that actually there's so much in the box but it interacts with so much of the outside world in so many different ways that it's less a cage and more like a tardis a party an adventure of some kind that quite literally contains the ingredients for every chef's kitchen that's ever existed the words of every writer and everything they've ever written the code that every computer program uses in the world there's so much to play with in here but for those three billion pairs those base pairs of ingredients that we have in here there are then six billion others in the world seven billion nine billion now to play around with to interact with not to mention the genes and the dna and every other species flora and fauna and the rest of the natural world itself so i find that not closed up but actually quite open and exciting okay i'll leave you with a quote from the early 20th century psychologist william james that i think is even more pertinent in the light of epigenetic discoveries compared with what we ought to be we are only half awake our fires are damp but our drafts are checked we are making use of only a small part of our physical and mental resources stating the thing broadly the human individual lives far within his limits thank you as always for watching and a huge thanks of course as always to my patreons without which this just wouldn't be possible so if you want to see scripts if you want to chat in the discord server if you want your name in the credits but most of all if you just want to help support make this content then click the link in the description below if not you can like you can share you can leave a comment all those things that help the algorithm thank you so much and i'll see you next time

Channel: Then & Now

Views: 119,323

Keywords: nature nurture, psychology, epigenetics, philosophy, dna, genetics, early intervention, politics

Id: LWixXFB9l6c

Length: 36min 5sec (2165 seconds)

Published: Thu Jan 06 2022