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The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. In the absence of a Y chromosome, the fetus will undergo female development. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. [5]
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.
Human history or world history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers . They migrated out of Africa during the Last Ice Age and had spread across Earth's continental land except Antarctica by the end of the Ice Age 12,000 years ago.
Sex differences in human physiology are distinctions of physiological characteristics associated with either male or female humans. These differences are caused by the effects of the different sex chromosome complement in males and females, and differential exposure to gonadal sex hormones during development.
Human female mating competition is complex and multifaceted and varies across cultures, societies, and individuals. [94] Females may compete for high-quality mates who possess traits that indicate underlying genetic quality, possibly including physical attractiveness and intelligence, [ 95 ] or material resources that can enhance the survival ...
Trump's executive order declares sex as "an individual's immutable biological classification as either male or female" and states that "gender identity" cannot be included in the definition of ...
[7] [11] In the 21st century, the noun female is primarily used to describe non-human animals, to refer to biologically female humans in an impersonal technical context (e.g., "Females were more likely than males to develop an autoimmune disease"), or to impartially include a range of people without reference to age (e.g., girls) or social ...