Editing Kin selection (section)

===Observational studies===
A study of food-sharing practices on the West Caroline islets of [[Ifalik|Ifaluk]] determined that food-sharing was more common among people from the same islet, possibly because the degree of relatedness between inhabitants of the same islet would be higher than relatedness between inhabitants of different islets.  When food was shared between islets, the distance the sharer was required to travel correlated with the relatedness of the recipient—a greater distance meant that the recipient needed to be a closer relative.  The relatedness of the individual and the potential inclusive fitness benefit needed to outweigh the energy cost of transporting the food over distance.<ref>{{cite journal |last1=Betzig |first1=L. |last2=Turke |first2=P. |year=1986 |title=Food sharing on Ifaluk |journal=Current Anthropology |volume=27 |issue=4 |pages=397–400 |doi=10.1086/203457 |s2cid=144688339 }}</ref>

Humans may use the inheritance of material goods and wealth to maximise their inclusive fitness.  By providing close kin with inherited wealth, an individual may improve his or her kin's reproductive opportunities and thus increase his or her own inclusive fitness even after death.  A study of a thousand wills found that the beneficiaries who received the most inheritance were generally those most closely related to the will's writer.  Distant kin received proportionally less inheritance, with the least amount of inheritance going to non-kin.<ref>{{cite journal |last1=Smith |first1=M. |first2=B. |first3=C. |year=1987 |title=Inheritance of wealth as human kin investment |journal=Ethology and Sociobiology |volume=8 |issue=3|pages=171–182 |doi=10.1016/0162-3095(87)90042-2 |last2=Kish |last3=Crawford }}</ref>

A study of childcare practices among Canadian women found that respondents with children provide childcare reciprocally with non-kin.  The cost of caring for non-kin was balanced by the benefit a woman received—having her own offspring cared for in return.  However, respondents without children were significantly more likely to offer childcare to kin.  For individuals without their own offspring, the inclusive fitness benefits of providing care to closely related children might outweigh the time and energy costs of childcare.<ref>{{cite journal |last1=Davis |first1=J. N. |first2=M. |year=1997 |title=Evolutionary theory and the human family |journal=Quarterly Review of Biology |volume=72 |issue=4|pages=407–35 |doi=10.1086/419953 |pmid=9407672 |last2=Daly |s2cid=25615336 }}</ref>

Family investment in offspring among black South African households also appears consistent with an inclusive fitness model. A higher degree of relatedness between children and their caregivers was correlated with a higher degree of investment in the children, with more food, health care, and clothing. Relatedness was also associated with the regularity of a child's visits to local medical practitioners and with the highest grade the child had completed in school, and negatively associated with children being behind in school for their age.<ref>{{cite journal |last=Anderson |first=K. G. |year=2005 |title=Relatedness and investment: Children in South Africa |journal=Human Nature |volume=16 |issue=1|pages=1–31 |doi=10.1007/s12110-005-1005-4 |pmid=26189514 |s2cid=23623318 }}</ref>

Observation of the [[Dolgans|Dolgan]] hunter-gatherers of northern Russia suggested that there are larger and more frequent asymmetrical transfers of food to kin. Kin are more likely to be welcomed to non-reciprocal meals, while non-kin are discouraged from attending.  Finally, when reciprocal food-sharing occurs between families, these families are often closely related, and the primary beneficiaries are the offspring.<ref>{{cite journal |last1=Ziker |first1=J. |last2=Schnegg |first2=M. |year=2005 |title=Food sharing at meals: Kinship, reciprocity, and clustering in the Taimyr Autonomous Okrug, northern Russia |journal=Human Nature |volume=16 |issue=2 |pages=178–210 |doi=10.1007/s12110-005-1003-6 |pmid=26189622 |s2cid=40299498 }}</ref>

Violence in families is more likely when step-parents are present, and that "genetic relationship is associated with a softening of conflict, and people's evident valuations of themselves and of others are systematically related to the parties' reproductive values".<ref>{{cite journal |last1=Daly |last2=Wilson |first1=M. |year=1988 |title=Evolutionary social-psychology and family homicide |journal=Science |volume=242 |issue=4878 |pages=519–524 |doi=10.1126/science.3175672 |pmid=3175672 |bibcode=1988Sci...242..519D }}</ref> Numerous studies suggest how inclusive fitness may work amongst different peoples, such as the Ye'kwana of southern Venezuela, the Gypsies of Hungary, and the doomed Donner Party of the United States.<ref>{{cite journal |last=Hames |first=R. |year=1979 |title=Garden labor exchange among the Ye'kwana |journal=Ethology and Sociobiology |volume=8 |issue=4|pages=259–84 |doi=10.1016/0162-3095(87)90028-8 }}</ref><ref>{{cite journal |last=Bereczkei |first=T. |year=1998 |title=Kinship network, direct childcare, and fertility among Hungarians and Gypsies |journal=Evolution and Human Behavior |volume=19 |issue=5|pages=283–298 |doi=10.1016/S1090-5138(98)00027-0 |bibcode=1998EHumB..19..283B }}</ref><ref>{{cite journal |last=Grayson |first=D. K. |year=1993 |title=Differential mortality and the Donner Party disaster |journal=Evolutionary Anthropology |volume=2 |issue=5|pages=151–9 |doi=10.1002/evan.1360020502 |s2cid=84880972 }}</ref><ref>{{cite book |last=Dunbar |first=R. |year=2008 |chapter=Kinship in biological perspective |editor1=N. J. Allen |editor2=H. Callan |editor3=R. Dunbar |editor4=W. James |title=Early human kinship: From sex to social reproduction |pages=131–150 |location=New Jersey |publisher=Blackwell Publishing}}</ref>