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Scientists have learned why identical twins have different personalities
Last reviewed: 01.07.2025
According to a new study published recently by scientists from the Murdoch Children's Research Centre in Melbourne, Australia, differences in personality and responses to external stimuli in identical twins are primarily explained by different environmental influences during their development in the womb.
The researchers took samples from the placenta and found that the DNA structure, as is traditionally believed, is absolutely identical in identical twins. In other words, they have absolutely identical sets of genes that determine their development, appearance, and which, it would seem, should determine their behavior. However, at the same time, the scientists analyzed the content of chemical markers of substances responsible for gene expression, and here they discovered a surprise.
It turns out that identical twins have different gene expression, which the researchers say is due to different “events that happened to them while they were in the womb.”
"We have had evidence for a long time that identical twins can have different health conditions, character and even appearance. However, from a genetic point of view, the existence of this phenomenon is not so easy to explain, since such people have absolutely the same genes, they should not differ from each other in any way," notes the head of the study, Jeff Craig.
The researchers believe that differences in gene expression mean that although such people have the same genome structure, not all genes are “working” – some are active, while others are “sleeping”. This depends on the nutrients, their volume and time of receipt, which children receive in the womb through the placenta. Scientists also do not rule out the possibility that the character of such people may be influenced by nutrition in the first months of their lives.
The researchers also add that during their analyses they found virtually no cases where gene expression in people was the same, or even more similar.
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