You are human in an industrial city.

You are a baby

You, a baby, cry because you feel like it.

There used to exist babies — in previous generations — who did not cry. 

These babies died 
    when their needs weren't met 
    because people forgot about these babies existing.

The parents in the city have an urge to address crying babies because their parents did.

Your parents, grandparents, and siblings address your needs as you grow up.

Suppose you are a woman

You are now a woman of child-bearing age who is ovulating.

You do not decide to

have an increased urge to have sex [1].
find all men hotter, and exponentially for your sexual "type" [2].
direct more visual attention towards men you find attractive [3].
experience increased self-esteem and self-perceived sexual desirability [4], energy, and a more creative personality [5].
experience physical changes such as peaked facial skin redness (blushing) [6].

However, these subconscious actions occur without your awareness.

You can speculate these traits (of the menstrual cycle) exist because humans with these traits reproduced more than "humans" lacking these traits.

Suppose a man approaches you and engages in sexual intercourse with you.

There is a high chance you know this man from your marriage, which is an economic contract [7]. The contract is recognized by society, enforced by government law, and managed by the government.

You selected this man as the city's government grants you the autonomy to sign your own marriage contract. However, your choice is constrained by social class, educational institutions, and corporate structures that restrict your selection to partners of similar economic status.

You might moan during sex because

You feel like it.
This behavioral trait is inherited from a prior generation of humans' which implies that there is a reason to moan or a lack thereof (which effects reproduction potential) [8].
This behavioral trait might be inherited from an environment where the behavior was evolutionary advantageous, but now the vestigial behavior has no evolutionary advantage or disadvantage [9].

The man orgasms before you do. Then, he exits your body.

Suppose you have not been satisfied and continue to have sex.

You address this lack of satisfaction with the man who provides you with post-coital intimacy until you are satisfied.

There is a smaller chance you were not in a relationship with this man prior to sexual intercourse.

You find a private place to engage in a secretive sexual encounter with this man to protect your social stability (e.g., civil reputation, employment status, and financial stability) [9].

You have sex with this man despite the lack of relationship with him because you felt sexually attracted to him [10].

Suppose you have not been satisfied yet.

You might continue to have sex with this man by waiting for his refractory period to clear. You achieve an orgasm 40% of the time during these encounters (compared to 75% in a committed relationship) [11].
You might feel sudden frustration, mood swings, or localized disappointment if he leaves before you want him to [12]. You do not feel like contacting this man again if you can't separate sex from emotional intimacy, and you will feel like he is unreliable for a relationship [13].
You might end the interaction upon his exit. You clean yourself and exit the situation.

Suppose you have a primary partner or husband who is not this man.

You might initiate sexual contact with your primary partner or husband later.
- This subconscious action creates paternity confusion for your primary partner or husband, who maintains a high perception of paternity certainty based on his own physical interaction with you [14]. However, there is a small chance (estimated to be ~1% for wealthy relationships, ~2% for middle class relationships, and between 4% to 6% for working class relationships) the child is not his [14].
You might not initiate sexual contact with your primary partner or husband later.

You might be aware

Sperm can live up to 5 days inside your cervix, uterus, and fallopian tubes awaiting ovulation [15, 16].
The first sperm to your egg is not the winner [17].
Your egg has influence or choice over which sperm is accepted [17, 18].

You know who your child's biological father is only if you had sex with one man.

You ensure your husband feels like the child's biological father to secure your place in his household [7].

Your husband or job addresses your needs

as you are pregnant.
as you birth the child.
as you raise the child (within your marriage estate).

You address the needs of

yourself.
then, your certain children (from your marriage).
then, your primary partner.
then, your city (via taxes).

Suppose you are a man

You are a mature man who has a sexual urge.

You do not decide to

increase flow of blood to your penis.
increase the size of your testicles.
increase your heart rate, blood pressure, and breathing rate.
lubricate your urethra with fluid (colloquially called "pre-cum").

However, these subconscious actions occur without your awareness.

You can speculate these traits exist because humans with these traits reproduced more than "humans" lacking these traits.

Suppose you approach a woman and engage in sexual intercourse with her.

You might penetrate her in a thrusting motion because
    1) You feel like it.
    2) This behavioral trait is inherited from a prior generation of humans' which implies that there is a reason to thrust or a lack thereof (which effects reproduction potential).
	    a) a theory exists which asserts "a man's penis shape is designed to pull out other men's sperm and assist in sperm competition." \[18\]
        b) a more-recent  theory contradicts (a) by asserting "a man's penis shape is designed to perform a protective parting squeeze which secures the semen in the woman upon the man's withdrawal." \[19\]

You orgasm and enter the male refractory period.

Your penis reduces blood flow (colloquially called "becoming soft").
Your penis reduces blood flow and becomes hypersensitive to touch, while post-orgasm hormones eliminate your sexual urge. So, you exit her body.

You are not aware how many other men have had sex with the woman, but you are certain she hasn't had sex with anyone else because she is your wife. [9]

Your wife can work but is still incentivized to follow the terms of her marriage, which is an economic contract [7]. The contract is recognized by society and enforced by spiritual law.

The government may limit the amount of women you can marry to prevent conflict.

So, you are certain you have children with your wife.

You address the needs of

yourself.
then, your certain children (conceived in marriage).
then, their caretakers (your wife).
then, your city (via taxes).

Sources Used

[1] Arslan, R. C., Schilling, K. M., Gerlach, T. M., & Penke, L. (2018). Using 26,000 diary entries to show ovulatory changes in sexual desire and behavior. Journal of Personality and Social Psychology. https://www.mpib-berlin.mpg.de/press-releases/partner-choice-of-women

[2] Stern, J., Gerlach, T. M., & Penke, L. (2020). "Probing Ovulatory-Cycle Shifts in Women's Preferences for Men's Behaviors". Psychological Science. 31 (4): 424–436. doi:10.1177/0956797619882022. PMID 32130075. https://journals.sagepub.com/doi/10.1177/0956797619882022

[3] Anderson, U. S., Perea, E. F., Becker, D. V., Ackerman, J. M., Shapiro, J. R., Neuberg, S. L., & Kenrick, D. T. (2011). I only have eyes for you: Ovulation redirects attention (but not memory) to attractive men. Journal of Experimental Social Psychology. https://pmc.ncbi.nlm.nih.gov/articles/PMC3161129/

[4] Arslan, R. C., et al. (2023). Women feel more attractive before ovulation: Evidence from a large-scale online diary study. Evolutionary Human Sciences. https://pmc.ncbi.nlm.nih.gov/articles/PMC10427307/

[5] Galasinska, K., & Szymkow, A. (2022). Enhanced Originality of Ideas in Women During Ovulation. Frontiers in Psychology. https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2022.859108/full

[6] Burriss, R. P., et al. (2015). Changes in women's facial skin color over the ovulatory cycle are not detectable by the human visual system. PLOS ONE / University of Cambridge. https://www.cam.ac.uk/research/news/womens-faces-get-redder-at-ovulation-but-human-eyes-cant-pick-up-on-it

[7] Bowles, S. (2011). Cultivation, coevolution, and the emergence of property rights. Proceedings of the National Academy of Sciences. https://pnas.org

[8] Brewer, G., & Hendrie, C. A. (2011). Evidence to Suggest that Copulatory Vocalizations in Women Are Not Reflexive Responses to Orgasm. Archives of Sexual Behavior, 40(3), 559–564. https://springer.com

[9] Schacht, R., & Kramer, K. L. (2019). Are We Monogamous? A Review of the Evolution of Pair-Bonding in Humans and Its Contemporary Variation Cross-Culturally. Frontiers in Ecology and Evolution, 7, 230. https://frontiersin.org

[10] Gangestad, S. W., & Thornhill, R. (1997). The evolutionary psychology of extrapair copulations: The role of symmetry and physical attractiveness. Evolution and Human Behavior, 18(3), 169–188. https://ehbonline.org

[11] Armstrong, E. A., England, P., & Fogarty, A. C. K. (2012). Accounting for riffraff: Orgasm inequities in heterosexual hookups and relationships. Social Problems, 59(4), 435–462. https://oup.com

[12] Maczkowiak, J., & Ribeiro, F. S. (2020). Postcoital Symptoms in a Convenience Sample of Men and Women. Journal of Sex & Marital Therapy, 46(5), 415–424. https://nih.gov

[13] Provencal, N., et al. (2019). Women's Orgasm and Sexual Satisfaction in Committed Sex and Casual Sex: Relationship Between Sociosexuality and Sexual Outcomes. The Journal of Sex Research, 57(7), 817–826. https://tandfonline.org

[14] Larmuseau, M. H. D., van den Berg, P., Claerhout, S., et al. (2019). A Historical-Genetic Reconstruction of Human Extra-Pair Paternity. Current Biology, 29(23), 4102–4107. https://doi.org

[15] Mayo Clinic. (2026). Sperm: How long do they live after ejaculation? Mayo Clinic Expert Answers. https://mayoclinic.org

[16] Indira IVF. (2026). How Many Days Does a Sperm Live in a Female's Body? Conception & Timing Guide. https://indiraivf.com

[17] Fitzpatrick, J. L., et al. (2020). Chemical signals from eggs facilitate cryptic female choice in humans. Proceedings of the Royal Society B: Biological Sciences, 287(1928), 20200805. https://royalsocietypublishing.org

[18] Goetz, A. T., & Shackelford, T. K. (2006). Sexual coercion, ejaculate characteristics, and semen displacement tactics. Semen displacement as a sperm competition strategy.

[19] Klug, M., et al. (2023). Morphological and physiological assessments of the human glans penis and alternative evolutionary hypotheses. An Evolutionary Advantage of the Human Glans Penis.