The preserved remnants of parts of the body, like bones, teeth, and turtle shells in the fossil record provide information about ancient life.
In a recent study, researchers looked at the historical roots of one organ, the placenta, which is essential to pregnancy, using patterns of gene expression, or transcriptomics.
Evolution of Placenta in mammals
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The placenta is extremely invasive in some mammals, such as humans, and can penetrate the uterine wall to the maternal tissue.
The placenta barely touches the uterine wall in other mammals, as per ScienceDaily.
According to senior author Vincent J. Lynch, Ph.D., an associate professor of biological sciences at the University at Buffalo College of Arts and Sciences, there is also everything in between.
The placenta is extremely invasive in some mammals, such as humans, and can penetrate the uterine wall to maternal tissue.
The placenta barely touches the uterine wall in other mammals.
According to senior author Vincent J. Lynch, Ph.D., an associate professor of biological sciences at the University at Buffalo College of Arts and Sciences, there is also everything in between.
Their findings indicated that this placenta was intrusive and that mammals have repeatedly evolved non-invasive placentas.
This answers a question that has persisted for 150 years.
All alive mammals, except for marsupials and egg-laying monotremes, are eutherians, Lynch explains.
Eutherians have lengthy pregnancies during which the growing fetus causes the mother to experience a strong physiological response.
The group compared the genes that are involved in the uterus of different mammals during pregnancy to perform the analysis.
The scientists used their data to determine the appearance of ancestral mammalian placentas after discovering that all these gene expression profiles are associated with the amount of placental invasiveness.
About 20 species, including the egg-laying platypus, pouch-bearing marsupials, and several eutherian mammals that bear children to live young, were included in the study.
One drawback of the analysis is its small sample size; the authors noted in eLife that additional research on more species is required to assess the validity of the results.
According to him, understanding which genes are active in various species during pregnancy teaches us about how evolution functions.
However, it also explained what constitutes a healthy pregnancy and how things can go wrong.
Experts are identifying the genes that create the perfect setting for healthy human conceptions. This could lead to issues if those genetic mutations are not expressed properly.
Any mammal that has a placenta that develops during pregnancy and enables the flow of nutrients and wastes between both the mother's blood and that of the fetus, is referred to as a placental mammal (infraclass Eutheria), as per Britannica.
The true placenta of the placental mammal permits a longer phase of growth inside the womb's protective environment, which is thought to have contributed to the group's evolutionary success.
The first placental mammals appeared between roughly 163 million and 157 million years ago, during the Jurassic Period, according to fossil evidence.
All living placental mammals and their latest common ancestor are grouped in the clade Placentalia, according to some scientists.
Fossil evidence of extinct non-placental eutherians, which have been the ancestors of contemporary placentals, is grouped here to reduce confusion.
