Evolutionary explainations of parental invesment

• Males invesment in smaller than females.
• Man is only restricted on how many females ha can mate with, thus his reproductive ability.
• Man procuces a vast number of spems over a long period of time incurring few cost.
• He cannot be sure of paterety so his best strategy is to impregnate as many females as possible.

• Females investment is much larger.
• She produces revatively few eggs.
• fertile for a short period and bears the cost of pregnancy, childbearing.
• best strategy is to indulge in behaviours increasing survial chances of her children.

Paternal Certainty

• males are more likely to desert with internal fertilisation as he is unsure of parernity.
• maternal grandparents are certain grandchild is genetically related to them, paternal grangparents are not. more care and resource allocation will come from maternal grandparents.

Order of gamates release internal fertilisation gives male change to desert first. external fertislisation allows female the opportunity to desert first.

Monogamy. Where speices are born at an earlier stageof development, intensive childcare. Pair bonds tend to be exclusive and long lasting. Increasing chances of survival.

• Kreb and Davies 81' - reported it is not always true external fertilisation leads to paternal certainty. In sunfish, cuckoldry occurs during the females egg possitioning.
• Dawkins and Carlisle 76' - found 366/46 species where there is simulatenous gamate release and bo sexes have equal chance od deserting, it is the male who provided monoparental care. This refutes the evolutionary predication.
• Andersson et al 99' - looked at investments of fathers in college education of there biological and step children. Highest when fathers were living with the biological mother of the child. otherwise invesments were equal. This goes against the evolutionary theory. perhaps men invest in stepchildren to show ability as a resource provider, increasing attractiveness to females.

• reported males of some fish species release sperm first in a nest and then female lay her eggs.
• Male has first opportunity to dessert but males carry out the childcare.
• Goes against the idea of the orger of gametes relsease hypothesis.

• 30% maternal Grandparents (GP) had regular contact with there grandchildren.
• only 15% of parternal GP did.
• Supports predictions of paternal certainty.

• Males who demonstrate cues of possitive disposition to parental invesment were seen more attractive by females.
• Supports evolutionary expaination of parental invesment.