I have discussed and addressed the evolution of Homo sapiens sprinkled in several previous blogs, but have not how the entire mammalian population came to be. How did a planet that was ruled by an enormous beings who were a cross between reptiles and mammals become a planet where mammals are the most common? In the following blog I will discuss how and when the mammal evolved.
First thing is first, who, or what was the first mammal? It may seem unbelievable but the common ancestor of all living mammals today looked like a rodent (image below). “The scientists then worked with an artist to illustrate this ancestor. In addition to a furry tail, the researchers suggest the four-legged creature likely ate insects, weighed from 6 grams (about the weight of some shrews) up to 245 grams — less than half a pound — and was more adapted for general scampering than built for more specialized forms of movement, such as swinging from trees.” This small mammalian ancestor appeared about 200,000 to 400,000 years after the extinction of the dinosaurs, which when compared to how long it took humans to evolve (5 to 8 million years), it was as if they were just waiting for the extreme threat to go away. But how did what makes a mammal a mammal come along?
First thing is first, who, or what was the first mammal? It may seem unbelievable but the common ancestor of all living mammals today looked like a rodent (image below). “The scientists then worked with an artist to illustrate this ancestor. In addition to a furry tail, the researchers suggest the four-legged creature likely ate insects, weighed from 6 grams (about the weight of some shrews) up to 245 grams — less than half a pound — and was more adapted for general scampering than built for more specialized forms of movement, such as swinging from trees.” This small mammalian ancestor appeared about 200,000 to 400,000 years after the extinction of the dinosaurs, which when compared to how long it took humans to evolve (5 to 8 million years), it was as if they were just waiting for the extreme threat to go away. But how did what makes a mammal a mammal come along?
If you were to ask a child who was just learning about mammals they would tell you that mammals have hair. We do not have a grasp why all mammals have hair, but there is a theory which, after what is theorized what happened to the dinosaurs makes sense. The reason mammals have hair was to regulate temperature, or in the case of the mammalian ancestor, to keep warm. Another big sign an animal is a mammal is if they give live birth. Again, the drop in temperature after the incident that caused the extinction of the dinosaurs played a big part in this one as well. Mammals evolved from a reptile named synapsids. Let us say the mammalian ancestor laid eggs, she would risk dying from staying still whilst sitting on her eggs. With the live birth, the female mammal is free to move gather food, protect herself, along with a myriad of other tasks. Live birth is also a huge advantage to the take over of mammals because of the fragility of eggs as opposed to incubating the offspring in the womb.
The type of mammal that gives live birth (placental), is the type of mammal that is populating the Earth. We are currently in the “Age of Mammals,” which, as I stated earlier, started 200,000 to 400,000 (roughly 65 million years ago) after the “Age of Dinosaurs” came to an end. The synapsids were around millions of years before they evolved into mammals. “These reptiles arose during the Pennsylvanian Period (310 to 275 million years ago). A branch of the synapsids called the therapsids appeared by the middle of the Permian Period (275 to 225 million years ago).” In hindsight, evolving over a span of 100+ million years into a mammal, the evolution of humans is not so bad. That said, throughout these millions of years, the therapsids had to lose their scales thus growing hair (or fur), produce milk producing glands, and above all adapt to the changing times by having a uterus.
All that said, it really is not that hard to believe the mammalian ancestor was so small. If you were a new species, a completely new branch of animal, being small was the best to ensure your survival. Primates for example, our, chimpanzee's, gorilla's, lemur's, every primates out there, we are all closely related to tupaiids (tree shrews...image below). Even though our mammalian ancestor evolved from a reptile, modern mammals cannot in anyway be linked to reptiles, or to any other group. “Since it can be shown that each of the 32 orders of mammals are separate and distinct groups set apart from one another and from all other creatures by unbridged gaps, it seems evident that collectively as mammals they are set apart as well.”
The type of mammal that gives live birth (placental), is the type of mammal that is populating the Earth. We are currently in the “Age of Mammals,” which, as I stated earlier, started 200,000 to 400,000 (roughly 65 million years ago) after the “Age of Dinosaurs” came to an end. The synapsids were around millions of years before they evolved into mammals. “These reptiles arose during the Pennsylvanian Period (310 to 275 million years ago). A branch of the synapsids called the therapsids appeared by the middle of the Permian Period (275 to 225 million years ago).” In hindsight, evolving over a span of 100+ million years into a mammal, the evolution of humans is not so bad. That said, throughout these millions of years, the therapsids had to lose their scales thus growing hair (or fur), produce milk producing glands, and above all adapt to the changing times by having a uterus.
All that said, it really is not that hard to believe the mammalian ancestor was so small. If you were a new species, a completely new branch of animal, being small was the best to ensure your survival. Primates for example, our, chimpanzee's, gorilla's, lemur's, every primates out there, we are all closely related to tupaiids (tree shrews...image below). Even though our mammalian ancestor evolved from a reptile, modern mammals cannot in anyway be linked to reptiles, or to any other group. “Since it can be shown that each of the 32 orders of mammals are separate and distinct groups set apart from one another and from all other creatures by unbridged gaps, it seems evident that collectively as mammals they are set apart as well.”
Earlier I did state that to be a mammal live birth is a factor, but in the case of monotremes this does not apply. What I mean by this is that monotremes are mammals who lay eggs. The species that fall into monotremes are not many, in fact, there are only two; the platypus and the echidna. I mentioned placental earlier, aside from it meaning to give live birth, it also means “presence of a placenta, which facilitates exchange of nutrients and wastes between the blood of the mother and that of the fetus.” This, of course, does not apply to monotrems, but it also does not apply to marsupials, even though they, in a way, to give live birth. But no matter our differences, we are all mammals, and this is our age.
Please feel free to comment on what you thought of the blog, or other physical anthropological subjects you would like me to cover.
Please feel free to comment on what you thought of the blog, or other physical anthropological subjects you would like me to cover.
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