Editing Reproductive success (section)

==Humans==
Some research has suggested that historically, women have had a far higher reproductive success rate than men. Dr. Baumeister has suggested that the modern human has twice as many female ancestors as male ancestors.
<ref>{{cite web | title = 8,000 years ago, 17 women reproduced for every one man an analysis of modern dna uncovers a rough dating scene after the advent of agriculture. | first = Francie | last = Diep | name-list-style = vanc | date = March 2015 | work = Pacific Standard | url = https://psmag.com/environment/17-to-1-reproductive-success#.xen7f2esb }}</ref><ref name="Wilder">{{cite journal | vauthors = Wilder JA, Mobasher Z, Hammer MF | title = Genetic evidence for unequal effective population sizes of human females and males | journal = Molecular Biology and Evolution | volume = 21 | issue = 11 | pages = 2047–57 | date = November 2004 | pmid = 15317874 | doi = 10.1093/molbev/msh214 | doi-access = free }}
*{{cite press release |date=September 21, 2004 |title=Genes Expose Secrets Of Sex On The Side |website=ScienceDaily |url=https://www.sciencedaily.com/releases/2004/09/040920063537.htm}}</ref><ref>{{cite web | first = John | last = Tierney | name-list-style = vanc| title = Is There Anything Good About Men? And Other Tricky Questions | date = 20 August 2007| url = https://tierneylab.blogs.nytimes.com/2007/08/20/is-there-anything-good-about-men-and-other-tricky-questions/?_php=true&_type=blogs&_php=true&_type=blogs&_r=2 | work = The New York Times }}</ref><ref>{{cite web | first = John | last = Tierney | name-list-style = vanc| title = The Missing Men in Your Family Tree | date = 5 September 2007 | work = The New York Times | url = https://tierneylab.blogs.nytimes.com/2007/09/05/the-missing-men-in-your-family-tree/ }}</ref>

Males and females should be considered separately in reproduction success for their different limitations in producing the maximum amount of offspring. Females have limitations such as [[gestation]] time (typically 9 months), then followed by lactation which suppresses ovulation and her chances of becoming pregnant again quickly.<ref name=":0">{{cite book|title=On Fertile Ground A Natural History of Human Reproduction|last1=Ellison|first1=Peter | name-list-style = vanc |publisher=Harvard University Press|isbn=978-0-674-00463-4 |year=2001 |doi=10.4159/9780674036444 |oclc=435534359}}</ref> In addition, a female's ultimate reproductive success is limited due to ability to distribute her time and energy towards reproducing. [[Peter T. Ellison]] states, "The metabolic task of converting energy from the environment into viable offspring falls to the female, and the rate at which she can produce offspring is limited by the rate at which she can direct metabolic energy to the task"<ref name=":0" /> The reasoning for the transfer of energy from one category to another takes away from each individual category overall. For example, if a female has not reached [[menarche]] yet, she will only need to be focusing her energy into growth and maintenance because she cannot yet place energy towards reproducing. However, once a female is ready to begin putting forth energy into reproduction she will then have less energy to put towards overall growth and maintenance.

Females have a constraint on the amount of energy they will need to put forth into reproduction. Since females go through gestation they have a set obligation for energy output into reproduction. Males, however, do no have this constraint and therefore could potentially put forth more offspring as their commitment of energy into reproduction is less than a females. All things considered, men and women are constrained for different reasons and the number of offspring they can produce. Males contrastingly are not constrained by the time and energy of gestation or lactation. Females are reliant on the genetic quality of their mate as well. This refers to sperm quality of the male and the compatibility of the sperms antigens with the females immune system.<ref name=":0" /> If the Humans in general, consider [[Phenotype|phenotypic]] traits that present their health and body symmetry. The pattern of constraints on female reproduction is consistent with human [[Life history theory|life-history]] and across all populations.

A difficulty in studying human reproductive success is its high variability.<ref name="Sear_2016">{{cite journal | vauthors = Sear R, Lawson DW, Kaplan H, Shenk MK | title = Understanding variation in human fertility: what can we learn from evolutionary demography? | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 371 | issue = 1692 | pages = 20150144 | date = April 2016 | pmid = 27022071 | pmc = 4822424 | doi = 10.1098/rstb.2015.0144 | s2cid = 206161581 }}</ref> Every person, male or female, is different, especially when it comes to reproductive success and also fertility. Reproductive success is determined not only by behavior (choices), but also physiological variables that cannot be controlled.<ref name="Sear_2016" />

In [[man|human males]] of advanced age (≥40 years), [[male infertility|infertility]] is associated with a high prevalence of sperm [[DNA damage (naturally occurring)|DNA damage]] as measured by DNA fragmentation.<ref name = Das2013>{{cite journal |vauthors=Das M, Al-Hathal N, San-Gabriel M, Phillips S, Kadoch IJ, Bissonnette F, Holzer H, Zini A |title=High prevalence of isolated sperm DNA damage in infertile men with advanced paternal age |journal=J Assist Reprod Genet |volume=30 |issue=6 |pages=843–8 |date=June 2013 |pmid=23722935 |pmc=3696445 |doi=10.1007/s10815-013-0015-0 }}</ref>  DNA fragmentation was also found to be inversely correlated with [[sperm motility]].<ref name = Das2013/> These factors likely contribute to reduced reproductive success by males of advanced age.

The Blurnton-Jones 'backload model' "tested a hypothesis that the length of the birth intervals of !Kung hunter-gatherers allowed women to balance optimally the energetic demands of child bearing and [[foraging]] in a society where women had to carry small children and foraged substantial distances".<ref name="Sear_2016" /> Behind this hypothesis is the fact that spacing birth intervals allowed for a better chance of child survival and that ultimately promoted evolutionary fitness.<ref name="Sear_2016" /> This hypothesis goes along with the evolutionary trend of having three areas to divide up one's individual energy: growth, maintenance, and reproduction. This hypothesis is good for gaining an understanding of "individual-level variation in fertility in small-scale, high fertility, societies( sometimes referred to by demographers as 'natural-fertility' populations".<ref name="Sear_2016" /> Reproduction success is hard to study as there are many different variables, and a lot of the concept is subject to each condition and environment.