This blog post focuses on Stephen Gould’s theory of punctuated equilibrium to explain how evolution can occur abruptly and compares it with gradualism.
1809 was the year two individuals who would fundamentally change the world were born. These individuals were Abraham Lincoln and Charles Darwin. While Lincoln liberated black slaves from Westerners, one could boldly say Darwin liberated humans from God through his theory of evolution. Admittedly, this is a slight exaggeration, but it illustrates the immense upheaval Darwin’s theory caused when first proposed. The reason lies in the fact that Western culture was largely built upon Christianity. The theory of evolution, suggesting humans evolved from primates like apes rather than being created by God, was a theory that shook the very foundations of Western life. Evolution and creationism, which seemed utterly incompatible, fortunately coexist today in a balanced relationship.
Since Darwin introduced the mechanism of ‘natural selection’ in ‘On the Origin of Species’, there has been much debate over the strength of natural selection. Those who believe in the powerful force of natural selection are called ‘adaptationists’, while those who doubt its strength are called ‘anti-adaptationists’. ‘Darwin’s Table’ adopts a format where these two research groups debate and advocate their respective theories. Perhaps because adaptationists have received significant support over the past 30 years, their arguments sometimes convey a sense of the authority consciousness or slight stubbornness characteristic of an entrenched establishment. The author aims to represent the position of the anti-adaptationists, who effectively point out these flaws.
First, the leading figure representing the anti-adaptationists is Harvard University paleontologist Stephen Gould. His theories, differing from Darwin and the adaptationists, can be summarized into three main points.
The first is the ‘punctuated equilibrium theory,’ which posits that evolution can occur abruptly. This differs from Richard Dawkins’ ‘gradualism,’ which posits evolution occurs steadily at a slow pace. Simply put, if gradualism is like a 100-meter dash, punctuated equilibrium is like the long jump, involving varied tempos.
Second, it asserts that “evolution does not necessarily equate to progress.” While life, starting with the simplest organisms like bacteria, inevitably evolves into increasingly diverse structures over time, it is difficult to view this as true progress. In fact, even Darwin cautioned against viewing evolution as progress in ‘On the Origin of Species’. However, later evolutionists sought to position humans as the most advanced beings, and this soon succeeded, becoming a means to justify many destructive human actions.
Third, he argues that the evolution of life relies heavily on chance. Had an asteroid not struck Earth 65 million years ago, the dinosaurs dominating that era would not have gone extinct, and thus the age of mammals would never have begun. In this context, he predicts: “Rewind the tape of Earth’s history and play it back. There would be no beings like humans; an entirely different biota would have emerged.”
We have now examined Gould’s main arguments. From here on, I intend to focus intensively on the theory of punctuated equilibrium. As explained earlier, punctuated equilibrium is an evolutionary theory positing that the evolutionary pattern of sexually reproducing species is divided into periods of stasis, where little change occurs over most of the time, and periods of divergence, where rapid speciation occurs over relatively short periods. This theory differs from Dawkins’ gradualism.
“Dawkins advocates gradual evolution. Speciation refers to the process where a small, geographically isolated population evolves into individuals with traits entirely different from the parent population through reproduction. This theory supports the punctuated equilibrium hypothesis that evolution occurs abruptly. Dawkins presents fossils showing trilobites underwent gradual evolutionary processes, arguing that slow evolution is possible alongside abrupt evolution.”
This claim is profoundly flawed. Trilobites survived on Earth for over 200 million years, yet trilobite fossils discovered today, regardless of their age, exhibit identical structures and shapes. The fact that they did not evolve over this period of over 200 million years cannot be explained by gradualism. This tendency is not unique to trilobite fossils. If gradual evolution had occurred, intermediate forms between one species and its evolved counterpart should naturally be found. However, studying fossils discovered across various strata reveals that organisms are preserved without any change whatsoever. Moreover, numerous species exist that are called living fossils, having survived unchanged for tens of millions or even hundreds of millions of years: the coelacanth, the horseshoe crab, the nautilus, New Zealand’s tuatara, and the ginkgo tree. Darwin himself was aware of these facts, but he deliberately ignored them, citing the incompleteness of the fossil record as his reason.
In his book After Darwin, Gould presents evidence supporting punctuated equilibrium theory under the name bush theory. We learn about the evolutionary process of humankind starting in elementary school. It consists of three stages: Australopithecus africanus ⟶ Homo erectus ⟶ Homo sapiens. This was accepted as the established theory until new species called Australopithecus robustus and Homo habilis were discovered in the 1930s and 1970s, respectively. The two newly discovered species differed significantly from Australopithecus africanus in their upright posture and brain capacity, yet they coexisted during similar time periods. In fact, Homo habilis possessed a brain capacity twice that of Australopithecus africanus, reaching two-thirds of the brain capacity of modern adults. Furthermore, none of these three showed any significant evolutionary trajectory during their lifetimes. In other words, we, Homo sapiens, are not a predestined final masterpiece on the evolutionary ladder, but merely one successful side branch that thrived on the evolutionary shrub through countless prunings.
Some might criticize this argument as follows: “Even if intermediate species existed during gradual evolution, couldn’t they simply have failed to leave fossil evidence? Or perhaps they haven’t been excavated yet? Provide more scientific evidence.”
If such a criticism arises, I believe it would mean they themselves acknowledge the uncertainty of their theories, since many of their claims are also based on fossil evidence. Indeed, it is true that we previously struggled to adequately respond to this criticism. However, with the development of evolutionary developmental biology, known as “embryo-biology,” decisive evidence capable of answering this is being discovered one after another. During their research on fruit flies, developmental geneticists discovered that various mutations, such as the antenna-pedia mutation where legs grow on the head, arise from a problem in just one specific gene called a homeobox gene (Hox gene). In other words, a problem in a single gene can completely transform the entire body. Furthermore, homeoboxes (sets of homeobox genes) have been discovered in diverse organisms ranging from nematodes to elephants to humans, and it was even found that they possess highly similar sequences. Specific examples include the eyeless gene in Drosophila, the aniridia gene in humans, and the small eye gene in mice. These three genes each regulate eye development. When the mouse small eye gene was introduced into Drosophila, it induced Drosophila eye tissue rather than mouse eye tissue. Another example is the disstalis gene, which causes mutations in the outer legs of fruit flies, yet is used to create appendages in all organisms. Similarly, the tinman gene, essential for heart formation in fruit flies, was found to play a crucial role in heart formation in vertebrates. It is now understandable how humans and orangutans, despite having only a 0.1% genetic difference, evolved into entirely distinct species. So what regulates these genes? It is the protein known as transcription factors, the on-off switches for genes. When activated by external environmental stimuli, changes occur in the genetic toolkit (all genes responsible for animal development, including homeotic genes), causing organisms to undergo sudden transformations.
The absence of intermediate fossil evidence and the discovery of the genetic toolkit and its on-off switches through advances in evolutionary developmental biology provide strong evidence supporting Gould’s punctuated equilibrium theory. Scholars advocating for gradualistic evolution have failed to offer compelling counterarguments against this evidence, allowing punctuated equilibrium to gradually gain traction. The significance of punctuated equilibrium lies in viewing humans not as a special entity at the pinnacle of evolution, but as one being that emerged through the process of variation, just like other organisms. It is said that science must be value-neutral. However, under the purpose of establishing humans as the highest beings, existing evolutionary research findings provided legitimate grounds for human supremacy and white supremacy, justifying destructive human behavior and the actions of whites enslaving Asians and Africans. It is hoped that from now on, many scholars like Stephen Gould will emerge, conducting objective research through empirical data and scientific analysis.
