This is due to the tortuous birth canal and close correspondence of the size of the foetal head with the size of the birth canal in humans, which leads to difficult parturition, the second unique human aspect of birth. This is considered to be disadvantageous because the mother cannot meet the immediate needs of the infant after the head emerges [4]. It has been suggested that the occiput anterior emergence pattern accounts for the third uniquely human aspect of birth, that is, the birth is attended by other individuals, such as midwives, and mothers actively seek assistance in childbirth [4,5,7,9].
However, the above notion about human uniqueness is not entirely confirmed because there are few comparative data on birth in non-human primates [10].
Birth in non-human primates is generally a solitary event, and observers have had few chances to record births in the wild. In addition, the process of parturition is quick, and precise prediction of its timing is difficult.
Thus, it is extremely rare that observers are able to witness the event in close enough proximity to determine the mechanism of birth in captive settings. Here, we report the orientation of chimpanzee newborns when they emerge from the maternal birth canal based on the first clear video recordings of the births of chimpanzees.
Three births were observed. In the first case, Tsubaki was the mother and Natsuki was the offspring. In the second case, Misaki was the mother and Hatsuka was the offspring. In the third case, Mizuki was the mother and Iroha was the offspring. The three mothers were all primiparous. The offspring were all females. In all cases, the father was Loi, one of the group's males; paternity was confirmed by DNA analysis. Naturalistic observation of their behaviour while they were in the enclosure confirmed mating between females and males on the estimated day of ovulation.
Therefore, the date of conception could be estimated to be the day of the female's last ovulation. In the first case, Tsubaki was 8 years and eight months old on the day of conception. She was 40 kg at the time and 50 kg just before the parturition.
The gestation length was days. In the second case, Misaki was 8 years and nine months old on the day of conception. She was 40 kg at the time and 46 kg just before the parturition. In the third case, Mizuki was 11 years and zero month old on the day of conception.
She was 52 kg at the time and 55 kg just before the parturition. The body weights of the mothers, and the gestation lengths were all within normal ranges of the previous data on captive chimpanzees [11]. The body weights of the newborns could not be measured on the day of their birth because the mothers held the newborns, and we did not intend to intervene in the natural maternal behaviours. The body weights were measured at later times electronic supplementary material , and these data were within normal ranges for captive chimpanzees [11].
Oestrus is accompanied by reddening of the sexual skin on the rump and face. Peak fertility ovulation occurs 11 to 14 days after onset of menstruation in both species regardless of cycle length 26 to 29 days in rhesus; 26 to 38 days in cynomolgus. On reaching sexual maturity, males may become more aggressive and begin exploring away from the natal group. The breeding season in macaques varies in timing and length between species, locations and over time; breeding seasonality is less pronounced in cynomolgus than rhesus macaques.
Macaques mate promiscuously. Females give birth approximately every 1 to 2 years, from 3 to 20 years of age. Higher-ranked females reproduce more often, from an earlier age, and have higher infant survival rates. In captivity, macaques can live for over 25 years maximum recorded is 40 years. Females over 25 years of age experience menopause. Geriatric illnesses are rarely seen in wild populations, but geriatric captive macaques exhibit illnesses such as arthritis , atherosclerosis , cataracts , gum disease, cancer, diabetes and obesity.
Low ranking macaques are at higher risk of chronic psychosocial stress, leading to more health problems in old age. Prenatal development Infancy Yearlings and juveniles Adolescence and sexual maturity Adulthood Senescence. Male infant care from NC3Rs on Vimeo. In this video, an adult male rhesus macaque protects a young infant. Weaning tantrum from NC3Rs on Vimeo. In this video, the infant on the left tries to suckle from its mother, but is rejected.
Auntying from NC3Rs on Vimeo. In this video, a yearling carries its infant sibling, which cries and is then taken by their mother. Trevathan says there are still aspects of human labour that make it "unique, or at least very unusual". She adds that the orientation of the human infant still provides a compelling explanation for the evolution of midwifery in humans because "assistance definitely facilitates delivery when the baby comes out in that position".
She also thinks her arguments have often been misinterpreted. Trevathan thinks that the pertinent question is not why humans have evolved midwifery, but rather why chimps have not. Although the study does not tackle that question, it certainly helps to quash the outmoded idea that humans are distinct from the rest of the animal kingdom.
Hirata, S. Trevathan, W. Download references. You can also search for this author in PubMed Google Scholar. Reprints and Permissions. Milton, J. Chimps give birth like humans. Animals Climate change is shrinking many Amazonian birds.
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