A new study led by Western Washington University suggests that sister city relationships have been around for longer than we thought.
Jack H. McBride and Tesla A. Monson conducted a comprehensive study of primate offspring numbers using life history data from 155 primate species and offspring numbers from an additional 791 mammal species. Image by Jason Brougham.
“Nearly all primates give birth to a single litter,” say Tesla Monson, a professor at Western Washington University, and Jack McBride, a doctoral student at Yale University.
“However, some genera, such as marmosets, tamarins, lemurs, lorises, and galagos, regularly give birth to twins or triplets.”
“Although humans most often give birth to singletons, twin pregnancies occur naturally at a rate of approximately 1.1-1.5% worldwide.”
“Advances in assisted reproductive technology have increased twin birth rates to around 3% in some areas over the past 50 years.”
“There is an urgent need to understand the impact of twins on pregnancy, mothers, and newborns.”
In this study, the authors collected data on reproduction and body size from nearly 1,000 different mammalian species to investigate the evolutionary history of twinning in primates.
The traits they analyzed included offspring size (number of offspring), gestation period, body size, and lifespan.
Contrary to previous assumptions, the analysis demonstrates that the earliest primates likely gave birth to twins.
The researchers also found that birth size and gestational age (the length of pregnancy) were closely related.
“Animals that give birth to more pups on average tend to have shorter gestation periods,” Professor Monson said.
“This also applies to humans. In the United States, full-term twins are considered to be born at 38 weeks, not 40 weeks, and many twins are born earlier than that.”
“This may be related to maternal energy limitations.”
“The next step is to look more broadly at offspring number across mammals and see which other reproductive, brain, and body size traits are associated with twinning.”
“We are particularly interested in understanding the relationship between twinning and tooth morphology.”
“For me, teeth are always a concern.”
of study Published in a journal human.
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Jack H. McBride & Tesla A. Monson. 2024. The evolution of offspring number in primates. human 4 (3): 223-238; doi: 10.3390/humans4030014
This article is based on a press release from Western Washington University.
Source: www.sci.news
