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The human brain. Differences in male and female brain size are relative to body size. [83] Early research into the differences between male and female brains showed that male brains are, on average, larger than female brains. This research was frequently cited to support the assertion that women are less intelligent than men.
The embryo and subsequent early fetus appear to be sexually indifferent, looking neither like a male or a female. Over the next several weeks, hormones are produced that cause undifferentiated tissue to transform into either male or female reproductive organs. This process is called sexual differentiation.
During puberty, a male's erect penis becomes capable of ejaculating semen and impregnating a female. [26] [27] A male's first ejaculation is an important milestone in his development. [28] On average, a male's first ejaculation occurs at age 13. [29] Ejaculation sometimes occurs during sleep; this phenomenon is known as a nocturnal emission. [25]
Among researchers who study puberty, the Tanner scale is commonly considered the "gold standard" for assessing pubertal status when it is conducted by a trained medical examiner. [5] In HIV treatment, the Tanner scale is used to determine which regimen to follow for pediatric or adolescent patients on antiretroviral therapy (adult, adolescent ...
When synthesized, these differences show that volume increases for males tend to be on the left side of systems, while females generally see greater volume in the right hemisphere. [5] On the other hand, a previous 2008 meta-analysis found that the difference between male and female brain lateralization was not significant. [25]
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
In Part Three, "Puberty", Harris touches on the transition of female and male bodies and feelings during puberty. [12] Harris explains the purpose of puberty as well as sharing information of what to expect and how to take care of the body. [12] In this part, she introduces masturbation as a result from sex hormones. [12]
Skeletons of female (left) and Male (right) black-casqued hornbills (Ceratogymna atrata). The difference between the sexes is apparent in the casque on the top of their bill. This pair is on display at the Museum of Osteology. Sexual dimorphism may also influence differences in parental investment during times of food scarcity.