How does evolution explain the relationship between brother & sister?

1) humans cultivate families and friends because we are herd animals. we feel the most comfortable having others to rely on in tough situations. lone humans are rare but of course do exist.

2) it is a genetic issue. if they mated and had children only once in a family group it would be unlikely for them to face the genetic consequences. it is when this becomes the norm that the genetic code starts to break down and become faulty.

Why do fruits or flowers on the same plant not attack each other, when their seeds are competing for the same soil?

Animals cooperate even when it is apparently not in their best interests as individuals.

Brothers and sisters who mate produce deformed child many times more often than unrelated parents.

Healthy close family members share the "Eeeeewwwwww gene"!

To even think about them sexually brings a huuuuge "Eeeewwwwwwww!!!!" response and the person focuses elsewhere.

There are unhealthy people, with defective or missing genetic material and, for them, laws are made.

Physical relations within family = 'devolve'!

Inter family = 'evolve'!

Litter mates are usually fond of each other. Inbreeding is shameful...you want to spread your blood line, not pollute it.

Inbreeding increase the risk of sterile or sickly children - shared mutations recombining.

It was more cultural and sexual mores (rules) than evolution that prescribe or affect relationships between siblings. Primary benefits of incest prohibitions were (1) healthier offspring when interbreeding is avoided and (2) more familial stability when sibling sexual activity is limited. Combined, these two results strengthened cultures with these values.

you are from the same people and have the same blood so basically u have some things the same and yeah... you guys r just meant to be close... i think this goes down to adam and eve

Before commenting anything on this subject one should understand the concept of creation of life.

Vedas say “Atmavai Puthra Namasi” meaning, when you reproduce, your soul is taking birth as your child

Life is a combination of body and soul representing Prakrithi and Purusha, created with the union of male and female. While male ignites life by passing a spark of his soul through sperm, female provides body through her egg and nourishes it.

When you have a son you are reborn as Purusha to pass on your soul to next generations. Just as plants sprout leaf after leaf to continue existence year after year your soul produces sons and grandsons to continue life generation after generation. Though bodies of off springs are different it is the same soul existing in all the sons and grandsons, called dynasty and is identified by surname.

When you have a daughter you are reborn as Prakrithi with all the beauties and energies of nature for assuming the role of a mother. When you give your daughter in marriage to your son-in-law, you are in fact gifting him your soul in the form of Prakrithi, for assuming the role of mother to his off springs. Mother being the supreme phenomenon of nature for continuation of life in the universe, Kanyadan is considered the utmost virtue.

Being off springs of the same person brother and sister have the same soul in them and have similar body cells created by the same mother. Hence they develop affection towards each other.

Sexual relationship needs attraction and chemical reaction. Since opposite poles attract and similar poles repel, there is no attraction between brother and sister. Even though the bodies are different with male and female organs they cannot mate since soul is the same and there is no chemical reaction. Since social customs and moral values forbid union between brother and sister it acts as a deterrent to control any misadventures by unscrupulous beings.

Even if they mate bodily keeping all these aside, the soul existing in both of them resists leading to malfunction of reproductive systems and deformities formed in children born out of such relationship. With the defective reproductive systems and deformities in off springs there is no future life and the soul perishes entering into a dark phase, called hell.