The correct definition of the anthropic principle states that humanity’s existence places severe constraints on the physical constants, structure, and history of the universe, on the Milky Way Galaxy, the solar system, and Earth and its life. Most lay-level astronomy books define the anthropic principle by stating that the presence of intelligent observers (beings capable of measuring astronomical bodies and phenomena) requires many characteristics of the universe and the laws of physics to be fine-tuned.
In an article written in International Journal of Modern Physics D, Brazilian physicist and astronomer Marcelo Gleiser1 points out that what is referred to as the “anthropic principle” in the astronomical research literature almost always amounts to nothing more than the “preconditions for primitive life.”2 These preconditions are the minimum physical and chemical circumstances necessary for prebiotic chemistry to become even a feasible possibility. Consequently, Gleiser suggests, “what is currently called the ‘anthropic principle’ should instead be named the ‘prebiotic principle.’”3
In his paper, Gleiser demonstrates that transitioning the universe’s ability to sustain living things from one stage of life to another is far from trivial. It’s no small feat to transition a universe from sustaining prebiotic chemistry to supporting single-celled life-forms. Moving on to support complex, multicellular organisms replete with appendages and internal organs is much farther yet from trivial. Likewise, it is an even more dramatic step in fine-tuning requirements to transition to a universe that allows the equivalent of the human species to thrive in a high-technology civilization.
Gleiser has confirmed, in part, what we at Reasons to Believe have claimed and demonstrated now for over two decades. In an electronic compendium to my book More Than a Theory I show the different levels of known fine-tuning of the universe, galaxy, planetary system, and planet needed for six different categories of life. The simplest bacterium requires fine-tuning of at least 501 different cosmic features in order to exist for at least ninety days somewhere within the universe. Meanwhile, human existence requires the fine-tuning of more than 824 different known cosmic features. In other words, based only on what we know so far and assuming the universe exists with all observable gross features and laws of physics, the probability of existence for an astronomical body capable of sustaining human beings would exist, without invoking divine miraculous interventions, is 10739 times more remote than it would be for a body capable of supporting bacteria for only 90 days. (Even that probability—of a body capable of supporting bacteria for only 90 days—is extremely remote, less than one chance in 10311.)
A probability 10739 times more remote is difficult for most laypeople to visualize. The 50 billion trillion stars that exist in the universe = 1023. All the protons and neutrons that exist in the universe = 1079. You have a better chance of winning the California lottery 140 consecutive times where you purchase just one ticket each time than of getting a human-life-supporting planet or moon via naturalistic means! This 140 consecutive times is 100 more than it would be for an astronomical body capable simply of supporting bacteria for 90 days or less.
Gleiser is right. By redefining the anthropic principle to be much less than it really is, the principle is robbed of much of its theological impact. Restoring the anthropic principle to its correct definition forces one of the most compelling evidences for a supernatural, super-intelligent Designer upon the scientific community and society at large.