Will human sperm be lost in microgravity?

Adriana Bos-Mikich

Department of Morphological Sciences, ICBS, Federal University of Rio Grande do Sul, Brazil

The growing global interest in space programs, including space colonization strategies, will necessarily have to consider the reproductive process in outer space. Humans procreate through sexual reproduction, a near ubiquitous feature of living organisms on Earth. Furthermore, sexual reproduction is the fundamental strategy through which living organisms colonize new environments, as proven by Darwin´s theory of evolution. Successful colonization in a new niche represents the selection of adaptation-advantageous traits in well-adapted individuals and the elimination of those that do not express these advantageous characteristics. The individual advantageous/non-advantageous variability is achieved by new genetic combinations that occur during the formation of sex cells, a process called meiosis, which is unique and essential to sexual reproduction. In addition, the interaction between male and female gametes, leading to fertilisation and the creation of a new human being, is a critical feature of human reproduction. 

Male and female sex cells must join together to form a new individual, the zygote, however, living circumstances in outer space may not provide favourable conditions for male and female gametes to join together naturally. In addition, the highly developed physiological mechanisms involved in human sexual reproduction may not be as effective when subject to a new environment, such as would be experienced if humans colonised another planet. Moreover, the effects of the high levels of radiation observed in space and microgravity on mammalian reproduction are largely unknown. In view of these difficulties and uncertainties, it is quite likely the use of assisted reproduction technologies, known as fertility treatment, will need to be considered for this fundamental issue of future lives spent in space stations or other planetary habitats.

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