Abstract Assisted reproductive technologies (ART) are commonly used to address human infertility and to boost livestock production. During ART, procedures such as in vitro fertilization, artificial insemination, and intracytoplasmic sperm injection introduce gametes and embryos to unnatural and potentially stressful conditions that can influence offspring health, often via epigenetic effects. In this perspective we summarize these key risks of ART for embryonic and longer-term offspring fitness, emphasizing the need for experimental research on animal models to determine causal links between ART and offspring fitness across multiple generations. We also highlight how ART can bypass a range of naturally and sexually selected mechanisms that occur in the female reproductive tract and/or via female secretions that ultimately determine which sperm fertilize their eggs. We further argue that this curtailment of female-modulated mechanisms of sperm selection may have important consequences for ART-conceived offspring. We encourage the development of ART methods that better mimic natural processes of sperm selection and embrace the fundamental principles of natural and sexual selection. Ultimately, the aim of this perspective is to encourage dialogue between the fields of evolutionary biology and applied areas of animal and human reproduction.
reproduction takes place by internal fertilization via sexual intercourse, but can also occur through assisted reproductive technology procedures. The average gestation
Humans (Homo sapiens, meaning 'thinking man' or 'wise man') are the most abundant and widespread species of primates, characterized by bipedalism, minimal body hair, and large, complex brains enabling the development of advanced technology, culture, and language. Humans are highly social beings and tend to live in complex social structures composed of many cooperating and competing groups, from fa
Most human reproduction takes place by internal fertilization via sexual intercourse, but can also occur through assisted reproductive technology procedures. The average gestation period is 38 weeks, but a normal pregnancy can vary by up to 37 days. Embryonic development in the human covers the first eight weeks of development; at the beginning of the ninth week the embryo is termed a fetus. Humans are able to induce early labor or perform a caesarean section if the child needs to be born earlier for medical reasons. In developed countries, infants are typically 3–4 kg (7–9 lb) in weight and 47–53 cm (19–21 in) in height at birth. However, low birth weight is common in developing countries, and contributes to the high levels of infant mortality in these regions.
Compared with other species, human childbirth is dangerous, with a much higher risk of complications and death. The size of the fetus's head is more closely matched to the pelvis than in other primates. The reason for this is not completely understood, but it contributes to a painful labor that can last 24 hours or more. The chances of a successful labor increased significantly during the 20th century in wealthier countries with the advent of new medical technologies. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the world, with maternal death rates approximately 100 times greater than in developed countries.
Both the mother and the father provide care for human offspring, in contrast to other primates, where parental care is mostly done by the mother. Helpless at birth, humans continue to grow for some years, typically reaching sexual maturity at 15 to 17 years of age. The human life span has been split into various stages ranging from three to twelve. Common stages include infancy, childhood, adolescence, adulthood and old age. The lengths of these stages have varied across cultures and time periods but is typified by an unusually rapid growth spurt during adolescence. Human females undergo menopause and become infertile at around the age of 50. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to…
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