Book Reviewed: Beasts Before Us: The Untold Story of Mammal Origins and Evolution by Elsa Panciroli

The extinct mammals Humans and dinosaurs co-exist in the cartoon world of the Flintstones. In a similar fashion, the mammalian ancestors shared their history with the Tyrannosaur Rex and related dinosaurs before the K-Pg mass extinction sixty-six million years ago. Some of these mammalian species included placental mammals that survived the catastrophic extinction. The surviving mammalian species, after the catastrophic event, rapidly diversified which was spurred on by the death of dinosaur predators, and emerging environmental factors that offered new opportunities. Two groups of animals existed in the late carboniferous period, between 320 and 315 million years ago, they were synapsids and sauropsids. The sauropsids are ancestral reptiles and some of these species evolved into birds. and synapsid evolved into mammalian species. The Cretaceous–Paleogene (K–Pg) extinction event is the mass extinction of most plant and animal species on the planet about sixty-six million years ago when the Chicxulub impactor, a plummeting asteroid or comet, seven miles long, hit the planet that brought an abrupt and calamitous end to most species. The evolution of mammals’ centers on the shapes of the teeth, the evolution of the middle ear bones, fur, hair, warm-bloodedness, and proportionally larger brains than reptiles of similar size. Mammals could chew food, and hunt carefully. They had mouse-like earflaps for detecting sound that provided advantage, helping them avoid predators and communicate with one another in new ways for competing and caregiving. These changes increased brain size. Not only did more grey matter help them learn information from the senses, but they could also compute emerging behaviors. Their teeth also helped in digging. The mammalian ability to feed underdeveloped offspring on milk increased the survival of litter. Bipedalism is the basic adaptation of the hominid which is responsible for skeletal changes. The earliest hominin species, and non-bipedal knuckle-walkers (the gorillas, and chimpanzees), evolved from a common ancestor, Sahelanthropus or Orrorin species, about six million years ago. The bipedal hominin species underwent further evolution into the Homo Sapiens who are around 250, 000 years. The author briefly discusses the revolution in methodologies and new techniques in the field of paleobiology that estimated the origins of ancient mammalian species. Fossil records and ancient skeletons are the principal sources for studying the history living species, but now they compute enormous datasets of bone shapes, and estimate the form and function mathematically, similar to the methods used in evaluating the strength of building materials. This technique has helped paleobiologists learn the evolutionary history of mammals. There has been a radical transformation in the science of extinct life. The anatomy of various species is put together and predicted how animals emerged into distinct groups. My only gripe about this book is that discussions in some chapters are not stimulating, and there are no photographs and few illustrations.