Twin studies show this. Twins who have had the same upbringing can be different, but twins who do not have the same upbringing and are adopted can be similar.
Minnesota Study of Twins Reared Apart (MISTRA) – An argument for nature.
In this study, researchers focused on the tale of identical twins who were separated at birth and adopted by different families. It wasn’t until they were 39 that they met, and they were surprised to find they both suffered headaches, bit their nails, smoked Salems, took up woodworking and even vacationed on the same beach in Florida. www.scpr.org (2012)
The study by researchers from Edinburgh University also suggests nature has a greater impact on development. The researchers found identical twins were twice as likely as non-identical twins to share the same personality traits. They said their DNA had the greatest impact.
Research has demonstrated that genes can change, identical twins with the same genetic inheritance can turn out completely different and the impact of environmental influences can be passed down the generations. www.independent.co.uk (2012)
Abi and Brittany