My answer: This is a famous and oft repeated question. Its origin usually is attributed to Charles Darwin who is claimed to have said, “From the fact that there are 500,000 species of beetles, the Creator, if he exists, must be inordinately fond of beetles.” The true origin of the question is the biologist John B. S. Haldane. In a speech Haldane gave to the British Interplanetary Society in 1951 and reported in volume 10 of the Journal of the British Interplanetary Society Haldane said, “From the fact that there are 400,000 species of beetles on this planet, but only 8,000 species of mammals, the Creator, if he exists, has a special preference for beetles.”
The not-so-subtle implication of Haldane’s statement is that a God who loves beetles more than he loves mammals appears to contradict the description of God presented in the Bible. When one considers the physics of beetles, however, Haldane’s statements proves precisely consistent with the description of God and his stated goals presented in the Bible.
Psalm 104, the longest and most detailed creation psalm in the Bible, describes God packing Earth with as much life as physically possible and with as great a diversity of life as physically possible. We humans are the beneficiaries of this creation strategy. It is this strategy practiced by God over billions of years that has endowed us with over 76 quadrillion tons of biodeposits—limestone, marble, coal, oil, natural gas, etc. that we can use to launch and sustain global high-technology civilization and use that civilization to take the good news of salvation through Jesus Christ to billions of human beings.
Given God’s goal of packing Earth with as much life as possible and as diverse as possible, the physics of Earth and beetles mandates that God will create many more species of beetles than of mammals. The number of species on Earth has been steadily increasing since the origin of life some 3.8 billion years ago. God created humans on Earth when the number of species of life he had placed on Earth had reached the theoretical maximum permitted by the laws of physics God had chosen to govern the universe.
The physics of the universe and the physical characteristics of Earth determine what the maximum number of species will be for animals of different size scales. For an 8,000-mile-diameter Earth, the greatest theoretically possible number of animal species peaks for animals with adult body sizes equal to about one centimeter. The average adult body size for beetles is about one centimeter. Therefore, given God’s goal to pack Earth with as much life as possible and as diverse as possible, it should come as no surprise that there are so many species of beetles.
We should not be surprised either that at the time of the creation of humans there were only about 8,000 species of mammals. Given the diameter of Earth, the average body size of mammals, and the complex warm-blooded nature of mammals, Earth’s theoretical maximum carrying capacity for mammals is close to 8,000 distinct species.