It is a common joke that you have to obey gravity because IT’S THE LAW! This is true of evolution, as well.
The evidence for evolution is so massive and overwhelming that most people are now arguing about the relative importance of different evolutionary mechanisms. Is evolution governed by chance, mutation, reproductive strategies, or the hand of a Creator? Often, the answer depends on the scale of the evolution you are discussing.
In its broadest sense, evolution is the change over time in an open energy system (system is a generic word for almost anything you can think of) as it interacts with its environment. Since most energy systems are composed of smaller systems, and are also part of larger systems (the largest being space-time), evolution is proceeding at different rates and different scales everywhere you look. We can talk about the evolution of star systems, of weather systems, of plant life, and of humans.
In fact, evolution proceeds on many scales at the same time. Humans are part of a stellar evolution, a planetary evolution, an animal evolution, a species evolution and a personal evolution all at once! Stellar evolution gives us galaxies and stars and enough heavier atoms to coalesce into planets. Planetary evolution gives us a breathable atmosphere, enough moisture and environments in which we can thrive. Species evolution gives us our distinctive shape, instincts and abilities. Personal evolution combines the energy of the culture we live in and the influence of personal events to take us from helpless infants to mature, capable adults.
These are not simply past events, they are on-going processes. Although many believe that human evolution ended a while ago, evidence continues to mount that it is still occurring. For humans, for example, it was reported in June 2011 that each human child receives sixty new mutations from the genes of their parents. Each new child is more than the simple reshuffling of parental genes!
Comparing evolution of a star to evolution of humans can be tricky, because the scale is very different. But evolution is more than just another word for change; evolution has similar dynamics at every scale.
1. Every system has a environment
Every system has an environment, a context of outside forces in which change happens. A star lives in a galaxy, a cluster of galaxies, a super-cluster of galaxies. A tree lives in a forest, in an ecology, in a global weather pattern.
Everything in the universe exchanges energy with their environment. The nature of the energy exchange has a direct impact on the patterns in the system. This is as true of plants that get too much or not enough water as it is of humans reacting to the latest trend in popular culture.
Every changing system is part of a larger system undergoing change. It also contains smaller systems that are also undergoing change. Imagine a set of nested Russian dolls, except that each doll is always changing.
2. Every system has a history
What you can develop into depends in part on what you have been. In stellar evolution, helium and heavier atoms exist because hydrogen atoms came first. Earth’s oxygen-rich atmosphere is only possible because plants have used the sun’s energy to convert carbon dioxide into oxygen. Human embryos develop gills and a tail because those patterns were used by our ancestors at some point in the distant past. We would not be human without that ancestry!
3. Every system undergoes continuous fluctuation
In classical Newtonian mechanics, forces act on each other. The quantum view is deeper. In the quantum view, forces are created by quantum jitters, fluctuations in the quantum foam that give rise to particles and waves. The quantum jitters combine to create fluctuations in everything they create at larger scales, in ways that science does not yet understand, although fractals are an interesting possibility.
At the everyday level, earthquakes provide a good example of fluctuations. Earthquakes are not rare; they are, in fact, almost continuous. The United States Geological Survey (USGS) estimates that there are several million earthquakes each year.
Frequency of Occurrence of Earthquakes
|7 – 7.9||15|
|6 – 6.9||134|
|5 – 5.9||1319|
|4 – 4.9||13,000 (estimated)|
|3 – 3.9||130,000 (estimated)|
|2 – 2.9||1,300,000 (estimated)|
The USGS estimate of earthquakes less than magnitude 2 is very low. So low, in fact, that it is due to a lack of data collection, not earthquakes! The table, and many studies (see Schroeder’s Fractals, Chaos, Power Laws), support the notion that earthquakes are fractal, where frequency varies as a power (exponent) of magnitude.
Applying the power law shown in the table to smaller earthquakes, the number of earthquakes between 1.0 and 1.9 is likely to be in the range of 13 million. Earthquakes between .1 and 1.0 are likely to be in the range of 130 million.
What is true of earthquakes is also true of humans. The fractal rate of heartbeats extends over thousands of beats both asleep and awake. Similar behavior has been found in brain-waves and human walking patterns.
Everything is vibrating, even if we (mostly) take it in stride!
So far, we have seen that a system (generic word for almost anything that you can think of) has external fluctuations from its environment, and internal fluctuations in its energy patterns. The fluctuations can be small or large. The system has a history/structure which permits some changes but not others.
We are part-way to seeing why evolution is a law. To understand the rest, we’ll need another post exploring how fluctuations collide and combine, and why evolution is the flip side of one of the biggest laws around: The Second Law of Thermodynamics. As British astronomer Sir Arthur Stanley Eddington wittily said of the Second Law in The Nature of the Physical World:
“If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.”
There’s no getting around it. If you are going to get a handle on the universe at all, the Second Law, often called the Law of Entropy, is the five hundred pound gorilla in the room.