
Just a comment a bit off topic on the idea that people 'grow to be like each other' over a long relationship. Environmentally influencing factors such as the same nutrition, the same living environment etc may have a small effect in this direction, but I believe it more stems from peoples often (but by no means always) expressed tendancy to choose partners that physically resemble themselves in the first instance. This coupled with the above 'lifestyle' similarities will account for the sometimes seen similarities between old couples. How the animals fit in - people simply empathise with animals that look like them.