Opponents of the science of evolution sometimes claim that evolution is a “theory in crisis.” This claim has had traction among regular church goers, 39% of whom believe that scientists do not generally agree that humans have evolved over time. When respondents are restricted to white Evangelicals, that number goes up to 49%.1 Such beliefs do not reflect what scientists actually think. When scientists themselves were asked the same question, 99% agreed that humans have evolved over time.2 There is very little debate among scientists about the central idea of evolutionary theory: common ancestry (including human beings). It is the settled backdrop against which biological research takes place.Read more on polling data
But of course there are elements of the contemporary theory of evolution that are debated; that’s how science works. A good example of such debate is a prominent article in Nature in 2014 that asked, “Does Evolutionary Theory Need a Rethink?” A careful read of the article shows that none of the authors doubts that evolution has occurred; they simply disagree on how to weigh various complex mechanisms for evolutionary change over time. Think of such disagreements along the lines of the various denominations within Christianity: it is possible to disagree on and debate some of the finer points without calling into question the general framework. To understand a bit of this internal discussion, it will be helpful to categorize some of the evolutionary “denominations”.Read more on the Nature article
Our blog author, Michael Burdett, gave a thorough discussion of the Nature article in the following blog post.SEE ALSO:
One of the main difficulties with understanding the disagreements within evolutionary theory is that the labels are used differently by different groups and often not carefully defined. The term “Neo-Darwinism” has been used for over 100 years in different contexts. Today it is not always clear when it is being used in a historical sense or to label a position some scientists advocate today, and many people have given up using it at all.Read more on the history of Neo-Darwinism
According to Stephen Jay Gould, the term “Neo-Darwinism” was coined in the late 1800s by George Romanes to refer to the version of evolution espoused by August Weismann which emphasized natural selection over acquired characteristics as the mechanism of change.3 To prove his theory, Weismann famously cut off the tails from rats over many generations, showing that this “acquired” characteristic would not be passed on. But it was not yet understood how hereditary characteristics were passed on with minor variation, and this form of Neo-Darwinism went into decline.
Once Mendel’s theory of genetics was incorporated into evolutionary theory, Darwinism was revived and called “the evolutionary synthesis” or as Julian Huxley called it in 1942, “the Modern Synthesis” (more on this below). Neo-Darwinism is sometimes used to refer to the evolutionary theory of this era.
The standard history of evolutionary theory is Peter J. Bowler, Evolution: The History of an Idea (Berkeley: University of California Press, 1989).
When “Neo-Darwinism” is used now, it generally refers to a “reductive” or “gene-centric” version of evolution. That is to say, all evolutionary change—from minor adaptations to the development of new species—can be understood simply as a change in the DNA of a population of organisms. This is sometimes phrased as “change in allele frequency over time” (alleles are versions of genes; genes are certain regions of DNA). Understood this way, macroevolution is nothing but microevolution over longer stretches of time. The most prominent advocate of this position is Richard Dawkins, as exemplified in his book, The Selfish Gene.Read more on microevolution vs. macroevolution
These terms do not have precise biological definitions. Sometimes microevolution is used to denote change within a species, and macroevolution to denote change from one species into another. But this is difficult because there is also no clear definition of species, and especially because there are no clear dividing lines between species in their evolutionary development.SEE ALSO: Understanding Evolution: Theory, Prediction and Converging Lines of Evidence
Extended Evolutionary Synthesis vs. Modern Synthesis
Some scientists today support what is increasingly being called the “Extended Evolutionary Synthesis” (EES). They challenge the gene-centric idea that variation comes entirely from genetic mutation and that selection merely reflects changes in the frequency of genes. They claim instead that organisms—not genes—should be the focal point of evolution to better account for how organisms co-construct and co-evolve with their environments. On this view random genetic mutations and natural selection continue to play a vital role in evolution, but so do other factors. These include:
- Developmental bias: how the embryonic development of organisms biases ways in which changes in their forms can occur.
- Phenotypic plasticity: physiological variability that leads to flexibility in the appearance and function of organisms.
- Niche construction: the fact that organisms do not live in isolation from their environments, and they can affect the niche in which they live and so affect their survival chances.
- Extra-genetic inheritance: some aspects of inheritance do not act at the level of the building blocks of DNA, but involve modifications to the proteins that package DNA or even the transmission of social behavior through cultural evolution.
While the EES biologists think these additions to evolutionary theory are sufficiently important to warrant a renaming of the theory itself, many other evolutionary scientists disagree. They prefer the label “Modern Synthesis” as broad enough to encompass these and other developments in the theory of evolution since Darwin. This label also has a history, but those who use it today usually mean simply that evolution takes place through the general categories of variation and selection. Its proponents are content to allow research into specific mechanisms for these to proceed under this label without needing an “extension” to the theory.
Again, none of these groups denies common ancestry, but they do disagree about the extent to which major changes are required in how we think about evolutionary theory.Read more on EES and the Modern Synthesis
The most prominent group defending the Extended Evolutionary Synthesis has called themselves “The Third Way.” Their website gives further details along with the people and books associated with the movement.
The Modern Synthesis does not merely parrot the evolutionary science of 75 years ago when the term was coined. Some people use the term interchangeably with “Neo-Darwinism” but on the whole, there seems to be more flexibility among those today who use the label “Modern Synthesis” vs. today’s Neo-Darwinists.
At BioLogos we are concerned that those in the general public and Christians in particular have been misled about the nature of the disagreements between evolutionary scientists. There are very, very few PhD trained scientists in biology who doubt that evolution (including common ancestry) has occurred. We hear about some of these because (often well-intended) Christian leaders appeal to them for rhetorical effect. As Christians, we have a commitment to truth and we must present the facts accurately. While the science of evolution remains a vibrant field, with many things still to be discovered and disagreements about many details, it is not a theory in crisis.
Properly understood, evolution is a scientific theory about the development of life. It is consistent with Christian theology. Read More >
Evolution is a scientific theory supported by an incredible amount of evidence. Read More >
We affirm that the Bible is the inspired and authoritative word of God. We also accept the science of evolution as the best description for how God brought about life on earth. Read More >
Is evolution driven mainly by random genetic variation, or are there other factors at play? Michael Burdett reviews the scientific debate. Read More >
It is not a surprise that a scientific theory will address areas that are poorly understood: indeed, it is expected that theories, as they expand, will naturally have a frontier... Read More >
1 Percentage of U.S. adults who attend church at least weekly (and percentage of U.S. adult white Evangelicals) who say that scientists generally do not agree that humans evolved over time. Pew Research Center, “Strong Role of Religion in Views about Evolution and Perceptions of Scientific Consensus” (October 22, 2015). http://www.pewinternet.org/2015/10/22/strong-role-of-religion-in-views-about-evolution-and-perceptions-of-scientific-consensus/
2 Percentage of actively working PhD trained members of the American Association of the Advancement of Science who believe that humans have evolved over time (when restricted to scientists in biology/medicine, the percentage stays the same). Pew Research Center, “An Elaboration of AAAS Scientists’ Views” (July 23, 2015). http://www.pewinternet.org/2015/07/23/an-elaboration-of-aaas-scientists-views/
3 Stephen Jay Gould, The Structure of Evolutionary Theory (Cambridge: Belknap Press of Harvard University Press, 2002), p. 216.
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