Just some thoughts.
animals have different stratagies for caring of offspring. Quality (K) verses Quantity (r).
In r dominate species its not how you care for your kids its how many of them you can make, the best exaples of extreme r species are animals like sponges, oysters, and so on. They pump out millions of eggs and sperm and after that thier job is done. Without any further assistance of the 5 million eggs produced by the oyster for example only a few hundred will survive.
Lobsters are less r ... they carry thier eggs (hundreds of thousands of them) untill they hatch then the mothers job is done and the microscopic larva must fend for themselves.
This pattern continues throughout the animal kingdom, the more parental care involved the fewer offspring you have. Caring for offspring is difficult and it takes a lot of the parents time and effort... even placing the partents own life at risk. However the fewer children you have, the better care you can give them, the higher the survival rates for those children become.
Extreme K oriented species, such as us Humans, Apes and Elephants, have only one (relitively rarely more) child at a time. How often they do so varies and this is part of how we can see the evolution of human "love".
Chimps for instance have only one child at a time, the mother will not be fertile again untill her current child is old enough to fend for itself. This take about two years. Male chimps have little to do with thier offspring, and rival males are not above killing the infant to get mom "in the mood"... she also can't count on much help from the other females, they have problems of thier own. Thus Chimp reproduction while effective at producing high infant survial rates is slow.
The same goes for Elephants who have one child every five years... because this rate is so much slower than Chimps, Elephants came up with a way to improve thier childrens odds of survival. Once again males have little to do with the kids, but instead of leavin mom allone to fend for her child, her female relitives come to her aid. They will all share in looking out for the baby. Males are frankly emotionally unstable and are kept away from the infants. The baby can grow up and will (if female) stay with the herd for the rest of her life, over 60 years.
Extreme K has its problems and both the elephant and the chimp are facing extinction due to it. While you put so much time in effort into one child the death of that one child has a greater effect on the species as a whole. One plague can wipe out whole generations and threaten the whole species with extinction. One extremely effective predator (humanity) can kill healthy adults faster than they can be replaced by new generations.
Humans are the most successful of the extreme K species... the key to our success is our use of two parent care and group care.. and our tecnology. From a biological only perspective.. we are successful because while we breed slowly one child every few years, we can have multiple children of multiple ages at the same time. (my sister for instance had seven)
How do we do it, we have a better support system. Not only does the Father stick around to help but grand parents, aunts and uncles and so on help out.
Now what about altruism... well that is older than humanity as well. Care for the sick and elderly existed ammong the Neandertals, as evidenced by [font=Arial, Helvetica, sans-serif][size=-1]"Old Man of La Chapelle-aux-Saints" who dispite not having teeth survived for quite some time and by the Shandar finds... one of a man with a withered right arm and who had also suffered a crushing injury to his left eye that likely blinded him for at least a while, both injuries had healed... only possible if someone was helping him. Another Shandar individual had a piercing injury to his ribs and the wound showed signs of healing, though the fact that it didn't heal completly indicates that was what killed him... both individuals had been purposely and carefully burried.
Homo erectus also cared for his elderly and likely his sick... in [/size][/font][size=-1] Dmanisi a toothless skull was found, the bone around the teeth was grown in indicating he had been toothless for some time. Without teeth he would have needed help in eating and likely in getting food in the first place.
so at least altruism predates us... by careing for others you improve your species chances of survival...and if you care for others, others will in turn care for you.
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