Trivers (1972) “Parental investment is the investment a parent makes in an indiviual offspring that increases it’s chances of survival at cost of the parent’s ability to invest in other offspring. ” The beneifts of parental investment increases survival of the offspring which comes from survival of the fittest developed from the evolutionary theory. There are sex differences in parental investment because the initial investment made my females is a lot greater than male investment.
The female investment in each offspring is substantial. The gamte the female supplies is much bigger than the sperm from the male and the gamate has limited supply. A females reproductive life is alot shorter than a males at around 30 years. The females bond with the baby is much stronger before the birth as she carries the baby for 40 weeks and then has the option to breast feed the baby after birth which mains she is the childs main provide. In comparisson the males investment in offspring is relatively small.
The male has large amounts of sperm and is fertile for life, Each investment requires little time and energy and the best way to maiximise his reproductive sucsess is to have many matings with multiple female partners to carry on his genes. Maternal investment is an explanantion of why females invest so heavily prior to child birth (internal fertilization), but the reasons why females invest so heavily after childbirth are less obvious. One factor is the gradual increase in brain size over the last two million years,which has resulted in a more difficult childbirth (because of the enlargment of the skull).
The Essay on Widow Bird Female Male Fish
Finding good daycare can certainly pose a problem these days, unless, of course, you " re an African widow bird. When it comes time for a female widow bird to lay her eggs, she simply locates the nest of a nearbyEstrildid finch and surreptitiously drops the eggs inside. That's the last the widow bird ever sees of her offspring. But not to worry, because the Estrildid finch will take devoted care ...
To compensate for this difficulty, childbirth occurs earlier in development than is ideal, and so humans are born relatively immature compared to other animals. As a result, human are dependent on their parents until at least the teenage years. Human mother must carry their unborn child for nine months and, after birth, the infants of early humans would have been dependent on their mother’s milk for up to two years. Another explanation for the females larger investment is certainty of maternity unlike males, females can be certain that they are the true parent of their child.
On the otherhand paternal investment can explain why males invest less in their offspring. Human males are able to opt out of parental investment in a way that females cannot. By focussing more of their reproductive effort on courtship and copulation, they can afford to devote relatively little of their time to parental care (Daly and Wilson 1978).
Secondily the danger of cuckoldry plays a big role as males can never be completely certain that any offspring produced by a female is thiers; therefore run the risk of using up valuable resources looking after another man’s offspring.
Finally the shift from mating to parentiny can explain lower levels of investment. Given that some level of paternal investment is found in most human societies, it is almost certain that at some point in our evolutionary past men benefited by shifting some portion of reproductive effort from mating to parentiny (Lovejoy 1981).
In terms of research, parental investment theory is supported by Brase who found that males who demonstrate cues of a positive outlook to parental investment were seen as more attractive by females.
This supports the theory as it shows that women look for mates who are willing to invest in care and resources for their offspring. The theory is also supported by Geher et al (2007), who exposed 91 non-parent heterosexual undergraduates to various parenting related responses, and found that males had significantly increased heart rate when presented with scenarios that emphasised the cost of parenting. This supports the theory as it shows that males are biologically less prepared than females to confront issues associated with parenting.
The Essay on Is male more aggressive than female?
It is generally thought that human males tend to behave more violently and aggressively than human females – and it seems true. In United States, most of the homicides during 1980 to 2008 are males, representing 90% of the total number (United States Department of Justice, 2010), and it is also the trend in the whole world. The reason of the difference between man and female in violence is always ...
