I know many of you must be thinking this guy is deluded. But I have this theory since I was a kid. Is live birth a good evolution?
Most mammals give birth to live young, except for some mammals called monotremes who lay eggs. There are a few non mammals animals who give birth to live young too, but most of non mammals lay eggs.
There's a group of mammals called marsupials in which the female give birth to live young too but early in the pregnancy, the female has a pouch (marsupium) in which it rears its young through early infancy, so most of the young growth occurs in that pouch.
To give birth to live young, mammals need a period called pregnancy which varies from a few weeks to almost 2 years in some elephants and rhinoceros. A Human takes almost 9 months to do it. In that period the body suffers huge changes, and there are many risks associated to the pregnancy and the birth as well.
In the other hand, oviparous lay eggs, with little or no other development within the mother. This is the reproductive method of many fish, amphybians, reptils, birds and monotremes, most insect and arachnids.
The major risk involved in lying eggs is predation by animals that feed on eggs, which means parents need to be alert all the time. Some species lay eggs and leave them. But birds f.i. take care of the egg until the young is born, this process is called incubation, with a need of constant temperature.
So, the question is: Which method is the best? Live birth or laying eggs.
Most mammals give birth to live young, except for some mammals called monotremes who lay eggs. There are a few non mammals animals who give birth to live young too, but most of non mammals lay eggs.
There's a group of mammals called marsupials in which the female give birth to live young too but early in the pregnancy, the female has a pouch (marsupium) in which it rears its young through early infancy, so most of the young growth occurs in that pouch.
To give birth to live young, mammals need a period called pregnancy which varies from a few weeks to almost 2 years in some elephants and rhinoceros. A Human takes almost 9 months to do it. In that period the body suffers huge changes, and there are many risks associated to the pregnancy and the birth as well.
In the other hand, oviparous lay eggs, with little or no other development within the mother. This is the reproductive method of many fish, amphybians, reptils, birds and monotremes, most insect and arachnids.
The major risk involved in lying eggs is predation by animals that feed on eggs, which means parents need to be alert all the time. Some species lay eggs and leave them. But birds f.i. take care of the egg until the young is born, this process is called incubation, with a need of constant temperature.
So, the question is: Which method is the best? Live birth or laying eggs.
