It has been argued that today's population level show the world to be young. For example:
In fact, if a simple geometric growth rate is assumed (which was the assumption made by Charles Darwin in relation to his imagined "struggle for existence" in nature), it would only take about 1100 years-assuming 35 years per generation-to develop that present world population of six billion people. ...
All of which indicates that the evolutionary scenario, which assumes that human populations have been on the earth for about a million years, is absurd. The whole universe could not hold all the people!
How Populations Can Grow, Henry M. Morris, ICR
If the number of people on earth can be used to decide the age of the earth, then the number of mosquitoes on earth can be used too. If we assume that every mosquito lays every egg it is physically capable of, and that all eggs grow to maturity, then the world can't be five years old.
A female "sand dollar" can release 380,000 eggs per year. Therefore, given the world population of sand dollars, the earth can't be three years old.
Every human has E. coli bacteria in their gut. Bacteria reproduce by splitting in two, and they can do this every hour or so. Therefore, calculating backwards from the world population of E. coli, the earth must be five days old. It would only take about two weeks of dividing for a single E. coli to fill the whole universe, so therefore the universe is less than two weeks old.
Perhaps there is something wrong with this kind of argument ?
In reality, mosquitoes require food in order to manufacture eggs, and wild creatures usually have a pretty limited food supply. Nor do all mosquito eggs grow up to be adults: many are eaten by fish, and birds, and bats. They get killed by frost, drought and hurricane. In short, there are a whole lot of forces at work which keep down the the number of mosquitoes. The production rate of mosquitoes is roughly balanced against the destruction rate - a situation which is called equilibrium.
There are occasions when a species will have a short-lived population boom, and some species go through boom-and-bust cycles. But Darwin assumed that equilibrium is the normal state of affairs.
The number of humans is growing today because of modern agriculture, and modern medicine (which doubled the average human lifespan). But the historical growth rate was much lower, and the growth rate of pre-agricultural nomadic societies was near nil. Remember, nomads have no granaries to provide food during a drought, or after a plague of locusts has come through.