Ответы
Siblings often resemble one another for several reasons:
1. Genetics. Siblings share a large portion of their genes, since they inherit them from the same parents. The more genes two individuals share, the more likely they are to resemble each other physically. Identical twins, for example, share very nearly 100% of their genes, so they resemble each other very closely. Regular siblings, who share about 50% of their genes on average, often look quite similar as well, though not as much as identical twins.
2. Shared developmental environment. Siblings also share very similar developmental environments, especially in the womb and early childhood. They are exposed to the same hormones and nutrients in the womb, and experience very similar conditions as they develop, especially in early life. These shared developmental experiences also contribute to physical resemblance.
3. Learning from parents. Siblings also tend to resemble each other in appearance because they learn things like posture, facial expressions, speech patterns, and other mannerisms from the same parents. They often dress alike or in a similar style based on what their parents choose. All of these shared learned behaviors also increase the resemblance between siblings.
4. Perception and familiarity. We also tend to perceive siblings as more physically similar than they really are, simply because they are so familiar to us. We get very used to their faces and features, and our mind amplifies the similarities and diminishes small differences. This perceptual effect, known as the "mere-exposure effect," also contributes to the impression of strong resemblance between siblings.
In summary, genetics, shared environment, learned behaviors from parents, and perceptual effects all work together to make siblings appear quite similar, though siblings can still be quite different from each other in both appearance and personality. But a strong family resemblance is very common.