Evolution is a fundamental organizing principle of the living world. It is a theory that permeates all of biology. Evolution can explain the relationship between organisms and how biological traits arose. Evolution is a powerful and correct scientific approach. Yet our current understanding of evolution is incomplete. We are confronted with many open questions. I will discuss some of them in this article. I will also argue that a purely scientific interpretation of evolution does not constitute an argument against Christian theology, which holds that God is creator and sustainer of the universe. Science and religion are fundamental components in the search for truth. They should work together to solve the challenging problems that mankind is facing.
What is Evolution?
The basic idea of evolution is surprisingly simple. For evolution to occur we need a population of reproducing individuals. These individuals can be molecules, cells or multi-cellular organisms. During reproduction they pass on their information from parent to offspring. The information is encoded in form of a genetic sequence. Sometimes mutations occur and offspring end up with a slightly modified genome. Mutation generates novel variants and thereby produces genetic variation. The population does not consist of identical individuals, but instead there are different types. If some of those types reproduce faster than others, selection operates. The faster reproducing types increase in relative abundance. They outcompete the slower ones, which might face extinction.
Mutation and selection are the key components of any evolutionary process.
Time Line and Major Steps
Our universe originated 13.7 billion years ago. Our solar system is 4.6 billion years old. Most scientists believe that there was an origin of life on earth and that this happened about 4 billion years ago.
The earliest traces of bacterial life (procaria) on earth are 3.5 to 3.8 billion years old. Higher cells (eucaria), with a nucleus, more complex genetics and organelles, emerged around 1.8 billion years ago. About 600 million years ago these higher cells discovered complex multi-cellularity and gave rise to animals, fungi and plants. A few million years ago, one animal species discovered human language.
I would consider these to be the five major steps in evolution: (i) the origin of life; (ii) the origin of bacteria; (iii) the origin of higher cells; (iv) the origin of complex multi-cellularity and (v) the origin of human language. Bacteria discovered most of biochemistry, higher cells discovered unlimited genetics; complex multicellularity discovered intricate developmental processes and animals with a nervous system. Humans discovered language.
Human language gave rise to a new mode of evolution, which we call cultural or linguistic evolution. The enormous speed of human discovery and invention is driven by this new mode of evolution. An idea or concept that originates in one brain can quickly spread to others. Structural changes (memories) are imprinted from one brain to another. Prior to human language the most crucial information transfer of evolution was mostly in terms of genetic information. Now we have genetic and linguistic evolution. The latter is much faster. Presumably the collective information in human brains evolves at a much faster rate than any previous evolutionary system on earth. The growing world wide connectivity speeds up this linguistic evolutionary process.
Mutation, Selection and Cooperation
Mutation generates diversity, and selection acts on diversity. Selection is based on competition, but in the living world we also observe cooperation. Cooperation means that individuals help one another. A cooperator pays a cost for another individual to receive a benefit. Cost and benefit are measured in terms of fitness, which is rate of successful reproduction. Cooperation can occur among replicating molecules that form complex organizations such as the first cell. Cooperation can occur among cells. For example, in filaments of cyanobacteria some cells give up reproduction (they die) in order to feed others with nitrogen. Multi-cellular organisms are based on cooperation among individual cells. Cancer is a breakdown of cooperation, where cells revert to their primitive program of selfish replication. Eusociality is an important phenomenon where some animals become `workers’ or `soldiers’ in order to help other animals to reproduce. Human society is based on cooperation. We need the good will and help of others.
Therefore, cooperation is an important phenomenon in biology. I would argue that without cooperation there is no construction of higher levels of organization. Therefore, I propose to add cooperation as a third principle of evolution, besides mutation and selection.
The question arises: Why would natural selection favor cooperation? Why should one individual reduce its own fitness in order to augment that of a competitor? Natural selection should oppose cooperation. It turns out that specific mechanisms must operate for cooperation to be favored over defection. At present we know five such mechanisms.
(i) Direct reciprocity: there are repeated encounters between the same two individuals. I help you today, you help me tomorrow. (ii) Indirect reciprocity: there are repeated encounters in a group of individuals. Cooperators gain a good reputation and will receive help from others. (iii) Kin selection: cooperation occurs between close genetic relatives. (iv) Multi-level selection: competition occurs not only between individuals but also between groups. Cooperative groups might outcompete less cooperative ones. (v) Spatial selection: individuals interact in spatial situations, social networks or sets. Cooperators prevail by forming clusters. Neighbors help each other.
The recent appreciation of the importance of evolution of cooperation shifts the perspective of evolution from a purely competitive scenario to one that includes the possibility of cooperation and altruism. Cooperation is crucially involved in the construction of higher levels of organization in the biological world.
Some Open Questions in Evolution
Similar to most other scientific endeavors, our current understanding of evolution is incomplete. This statement is not meant as a criticism of the approach, but rather as an impetus for further work. I will list three interesting open questions.
1. The origin of life and the very beginning of evolution
Life can be defined as that which evolves. Living systems are the product of evolution and are capable of undergoing further evolution. But how does evolution begin? Evolution requires populations of reproducing individuals? But how do we obtain individuals that have the ability to reproduce? This question concerns the transition from chemistry to biology, from “prelife” to life.
Scientific explanation for this transition have been proposed, but they are not based on standard evolution. Evolution presupposes reproduction and therefore cannot lead to the origin of reproduction. Therefore, evolution is not a theory that explains the origin of life.
2. Why is evolution constructive?
Imagine our planet 3 billion years ago when it was populated by bacteria. How do we get from such a world to what we have now? Which properties of the bacterial cell suggest that there is “open ended” evolution ahead? An evolution that would lead to higher cells, complex multi-cellularity and even to intelligent life? What makes evolution constructive on large time scales? Where in the mathematical formalism of evolutionary dynamics, do we find its constructive power?
3. The search space
Evolution is a search process that explores a huge space of possibilities. But what generates that search space? Is a theory for that space not a deeper description of biology, than a theory which only describes the search process. You can say evolution discovers intelligent life, but it does not generate the possibility of intelligent life. What generates the possibility of molecules that store information, of cells that can divide, of multi-cellular organisms of human language? Ultimately the answer must come from the laws of physics and chemistry, but no scientist can do this right now.
God and Evolution
In Christian theology, God is the creator and sustainer of the universe. According to St. Augustine, God is atemporal and created the world ex nihilo (out of nothing). According to St. Thomas, God is the ultimate cause for everything that exists.
God has chosen to unfold his creation in time according to laws of nature. Humans, created in the image of God, have begun to understand some aspects of these laws of nature. Evolution is an organizing principle of the living world. God uses evolution to unfold life on earth. The creative power of God and the laws of evolution are not in conflict with each other. God acts through evolution. God is the ultimate cause for evolution. In this world view, without God there would be no evolution at all.
Similarly, God uses gravity to organize the structure of the universe on a large scale. Without God there would be no gravity. Neither gravity nor evolution constitute challenges for Christian faith.
A purely scientific interpretation of evolution does not lead to an argument against the existence of God. Scientific atheism is a metaphysical position, which goes beyond a scientific interpretation of the available evidence.
God is not only creator, but also sustainer. God’s creative power and love is needed to will every moment into existence. God is atemporal. In my opinion, an atemporal Creator and Sustainer lifts the entire trajectory of the world into existence. For the atemporal God, who is the creator and sustainer of the universe, the evolutionary trajectory is not unpredictable but fully known.
1. What makes evolution constructive?
2. Evolution is a search process. In order to succeed every search process requires a restricted search space.
What is a theory of the space that is being searched? Should we search for a “universal grammar” of life?
3. Evolution presupposes reproduction. Which process leads to the origin of reproduction?
My essay contained two parts. The first, longer part was about evolution and the role of cooperation in evolution. I discussed five mechanisms for the evolution of cooperation. I also pointed out some open problems in evolution, which are areas for current research. The second, shorter part was about the dialogue between Christian theology and evolution. Here I described God as the ultimate cause for everything that exists.
Fifteen comments were written, some of them were quite long. Important questions were raised. Several readers wrote more than one comment. George Gantz argued for a “cooperative rather than a confrontational dialogue” between science and theology, which I like very much.
A recurring question was whether cooperation requires intention. Intention is an important aspect of human cooperation. People distinguish between intention and outcome of an action. But intention is not really a concept, when cooperation occurs between cells. One cell produces a costly substance, which benefits other cells. Evolutionary game theory does not require intention. In this approach, “strategy” means behavior, but there need not be strategic thinking or intention behind it.
There was a discussion about protocells and whether our current understanding already explains the origin of life. For me the main open question is the following: evolution acts once we have reproduction with inheritance. Reproduction at different rates leads to natural selection. Inaccurate reproduction leads to mutation. But what is the organizing principle that operates prior to reproduction? What mechanism leads to the emergence of reproduction, to the onset of evolution? My research under the heading “prelife” is devoted to this question. Here I have formulated a generative chemistry that leads to the production of information prior to the emergence of reproduction (replication). Prelife is associated with “revolutionary dynamics”; there can be blunt selection in the sense that some information carriers become more important than others; there can be catalysis and mutation. Prelife is a system that seeks to explain the transition from chemistry to biology (evolution). We also study evolutionary dynamics in protocells and explore how protocells can select for enzymatic activity in RNA molecules.
An intriguing question was: what kind of matter can undergo evolution? My proposed answer is that currently we know of two types of evolutionary processes: genetic evolution and cultural evolution. Thus, the biological material in biopolymers, viruses and cells is subject to evolutionary change and also the products of human inventions, such as behaviors, tools, ideas and machines. I think the mathematical understanding of genetic evolution is more advanced than that of cultural evolution. There are many research opportunities in formalizing cultural (or linguistic) evolution.
Finally, I was intrigued by “blindboy’s” philosophical position that “existence needs no explanation”. I find it a calming position, an acceptance of facts. But is it compatible with the searching human mind? Is it not the case that we constantly seek for explanations that are of the form “why does X exist?”. Is the scientific quest not driven by the question why something exists? Why are there cells, viruses, animals, plants? What leads to the evolution of those structures? Why do planets and stars exist? What leads to their formation? Blindboy continues and says “… because non-existence does not exist.” But for certain mathematical equations there exists no solution. Proving the non-existence of solutions for certain equations can inspire mathematical research for centuries. In my experience, searching mankind continuously seeks to explain both existence and non-existence. Nevertheless, I find the question intriguing, because even the most critical mind takes many things for granted without being aware of them.
Two New Big Questions:
- Which matter in the universe can undergo evolution?
- Does existence require an explanation?