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Does the environment we are in affect who we are?

Updated: Mar 30, 2020

Nature or nurture? Why are we who we are?

By: Eliabel Legrand


There are two theories about how we get our traits, personality and become the person we are;

One is the theory that nature dictates personality, traits and behaviour are determined by genes and hereditary factors, that genes dictate these things from the day you are nothing and were thought to be unchangeable.

The other theory is the nurture theory, this is a popular theory that our environment and upbringing makes us who we are, and that genes don’t dictate everything, that the environment plays a role in who we are/become.

One being that we get our traits etc from genes, seen as an unchangeable blueprint that dictates everything about you from birth. You get your genes from your parents.

However the information found from the rat-licking study shows us that there is fact there is another path, to become who we are. This path is called epigenetics, which literally translates to ‘above genetics’. Epigenetics is the term for non-genetic influences on gene expression.


As a sign of affection and a way to nurture their babies, mother rats lick their rat babies. The rat pups who receive high amounts of licks at a young age and are highly nurtured then grow up to be calm and relaxed rats whereas baby rats who don’t receive many licks from their mother and aren’t nurtured very much or at all, grow up to be anxious and stressed adult rats. The anxious rats when they have pups of their own they generally also neglect and don't give many licks to their babies which then makes the pups grow up to be stressed and anxious and the cycle continues.

By licking her pup, a mother rat can write information onto her babies' genes. The epigenetic code allows certain information to be passed onto the offspring without it being passed on through genes. But the epigenetic is sensitive to changing with the change of environment conditions such as danger levels and food availability.

Another way they investigated if anxious behaviour is genetic/heredity is by taking a rat baby born of an anxious rat and gave it to a calm mother to bring up, the baby rat born of an anxious mother when grown turned out to be calm and relaxed, so took after its fostered/adopted mothers behaviour rather than its biological mothers behaviour. TThey also took a baby born of a calm, relaxed and high nurturing mother and gave it to an anxious, stressed and neglectful mother to raise, the pup when fully grown turned out to be stressed and anxious, taking after its stressed fostered mother rather its calm biological mother therefore proving that the behaviour is not genetic or hereditary it is epigenetic.

All newborn rat babies have clusters of molecules attached to their genes called methyl groups. Methyl groups when attached to a gene it silences it therefore cancelling out the behaviour and/or traits. Low nurtured pups grew up with the methyl groups still attached on the other hand the highly nurtured pups grew up and the scientists found that their methyl groups had disappeared. Meaning through the mothers licking behaviour she can remove the methyl groups from the genes of her baby, causing the gene to be unsilenced. The gene that the methyl groups are attached to and silence if not removed appear to be the reason behind whether a baby rat grows up to be calm and relaxed or stressed anxious.

Pups that receive high amounts of nurturing and licks grow up to care, nurture and lick their pups causing the offspring to grow and repeat the cycle. The difference between a stressed and anxious is not genetic, it is epigenetic, which means that stressed and anxious or calm and relaxed behaviour is not inherited and whether they are calm or anxious is dictated by the mother rat and how many licks and nurturing she gives the baby during its first week of life. The epigenetic pattern established by the mother in the pup tends to stay put throughout the rest of the rats life and is generally passed onto offspring and the cycle continues.

Gene expression patterns set up in rats first few weeks of life are not [necessarily] set in stone, as you can take a rat that was low nurtured and received very little amounts of licks and inject its brain with a drug that removes the methyl groups that makes the rat stressed and anxious ( the methyl groups are removed from calm rats by their mothers when they lick the baby ). It works in the opposite too, you can make a relaxed rat, inject it with methionine ( a source of methyl ) and make it anxious. Drugs affect many genes, so aren’t a substitute for maternal care. It has also been discovered that you can make an anxious rat more relaxed if you improve it’s living quarters.

When in an environment where food is abundant, and there is low levels of danger a relaxed rat will flourish, achieving a comfortable life, with a high social ranking, and the worry of where they can get food from is non-existent. However, on the contrary, a stressed and anxious rat won’t have as good of a run. The low nurtured rat will likely have a low social standing and may suffer from diabetes or heart disease, there is no clear reason why at the moment but inferences have been made with regards to this.

Although being anxious is viewed as being a negative thing however for rats being anxious does have its advantages.

In a different environment, the tables turn, as the anxious, hesitant behaviour of the low nurtured rat has an advantage in an environment where food sources are low and there are high danger levels, the low nurtured rat is more likely to keep under the radar and respond quickly to stressful situations. Whereas a relaxed rat, may be a bit too relaxed, and is more likely to let its guard down and get eaten by a predator.

So in situations where danger is high and food is scarce it pays off to be anxious.


This research helps us understand rats but as well as that the research helps us to understand human inheritance and helps us start to answer a question that has been thought by so many and is one of the great questions of humanity which is ‘what makes us?’ as well as settling the feud between whether it is ‘nature’ or ‘nurture’, this research shows that ‘nurture’ has a big impact on who we become.

If the baby rat is not licked during the first few weeks of its life it will grow up to be stressed and anxious whereas if receives lots of licks it will grow up to be calm and relaxed, as the licking behaviour removes the methyl groups on the genes. So a good mother rat is one that shows loving and nurturing behavior towards her young.


Cherry, Kendra. “The Age Old Debate of Nature vs. Nurture.” Verywell Mind, Verywellmind, 5 Feb. 2009, Accessed 5 Jan. 202AD.

Det medisinske fakultet UiO. “Epigenetics: Nature vs Nurture.” YouTube, 29 Jan. 2016,

“Epigenetic Definition - Google Search.” Google.Com, 2013, Accessed 5 Jan. 2020.

Extra Licking Makes for Relaxed Rats. “Extra Licking Makes for Relaxed Rats.” Science | AAAS, 12 Sept. 1997, Accessed 5 Jan. 2020.

“Lick Your Rats.” Utah.Edu, 2013, Accessed 5 Jan. 2020.

“Michael Meaney on Nature vs. Nurture.” YouTube, 15 July 2015, Accessed 5 Jan. 2020.


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