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The BioLogos Forum is designed to foster a serious and comprehensive discussion of Christian faith and the sciences. We believe that charitable engagement of different perspectives within the Church helps sharpen our thinking and deepen our commitment to the truth that is hidden in Christ. So while many of the articles and videos under the distinctive Forum banner come from BioLogos staff and Senior Fellows, we feature a range of voices, including those that disagree with us and with each other. Unless otherwise noted, views expressed are those of the authors, not necessarily of The BioLogos Foundation. You can read more about what we believe here, and join the conversation in the comments section at the end of each post.

Evolution Basics: A New Introductory Course on Evolutionary Biology

Evolution Basics

Written by BioLogos Fellow of Biology Dennis Venema, this series of posts is intended as a basic introduction to the science of evolution for non-specialists.
Evolution Basics: A New Introductory Course on Evolutionary Biology

Evolution Basics: A New Introductory Course on Evolutionary Biology

The goal of this course is straightforward: to provide evangelical Christians with a step-by-step introduction to the science of evolutionary biology. This will provide benefits beyond just the joy of learning more about God’s wonderful creation. An understanding of the basic science of evolution is of great benefit for reflecting on its theological implications.
February 07, 2013 
Dennis Venema 
Genetics, History of Life 
174
 
Evolution Basics: Evolution as a Scientific Theory

Evolution Basics: Evolution as a Scientific Theory

In common English usage, “theory” means something like “guess” or “hunch”. It means something speculative, uncertain. In science, however, the meaning is almost exactly the opposite. In science, a theory is an idea that has stood the test of time. This difference between the common usage and the scientific usage of the word is a frequent source of confusion for nonscientists.
February 21, 2013 
Dennis Venema 
History of Life 
132
 
Evolution Basics: Darwin’s Early Observations on Biogeography

Evolution Basics: Darwin’s Early Observations on Biogeography

For Darwin, both of these observations (that oceanic islands lacked terrestrial mammals, and that endemic species on islands were most similar to a species on the closest mainland) had the same explanation: his hypothesis that endemic, oceanic species were the modified descendants of a colonizing species from the nearest continent.
March 07, 2013 
Dennis Venema 
History of Life 
14
 
Evolution Basics: An Introduction to Variation, Artificial Selection and Natural Selection

Evolution Basics: An Introduction to Variation, Artificial Selection and Natural Selection

Rather than a breeder choosing which individuals to mate, the ability of different variants to reproduce in a given natural setting would allow some to reproduce at a greater rate than others. Since their traits would be heritable, this would drive changes in traits over time in the population experiencing “natural selection”, a term Darwin coined as an analogy to human, or artificial, selection.
March 21, 2013 
Dennis Venema 
Genetics, History of Life 
1
 
Evolution Basics: Artificial Selection and the Origins of the Domestic Dog

Evolution Basics: Artificial Selection and the Origins of the Domestic Dog

Here in the early 21st century we are beginning to see the genetic underpinnings of artificial selection at a genome-wide level, and the results are absolutely in keeping with Darwin’s ideas: that populations contain significant diversity, and that artificial selection can act on that diversity over time to promote the reproduction of certain variants over others, and thus shift average characteristics of a population.
April 04, 2013 
Dennis Venema 
Genetics, History of Life 
936
 
Evolution Basics: New Genes, A New Diet, and Implications for Dog Origins

Evolution Basics: New Genes, A New Diet, and Implications for Dog Origins

While the mutation that led to shortened legs in some dog breeds is a particularly dramatic example of a new variation arising (since it involves the birth of what is effectively a new gene), there were many other genomic regions selected during the creation of dog breeds. … the main theme is clear: small changes in DNA, combined with artificial selection, can add up to large changes in form within a population in a short amount of time.
April 05, 2013 
Dennis Venema 
Genetics, History of Life 
15
 
Evolution Basics: Natural Selection and the Human Lineage, Part 1

Evolution Basics: Natural Selection and the Human Lineage, Part 1

I’ve often encountered the misconception among non-biologists that mutations are always harmful, or always remove functions and information. However, in many cases mutations can be beneficial, add gene copies, and new functions and information to the organism as well.
April 18, 2013 
Dennis Venema 
Genetics, History of Life 
7
 
Evolution Basics: Natural Selection and the Human Lineage, Part 2

Evolution Basics: Natural Selection and the Human Lineage, Part 2

Variation, of course, is only one part of the recipe for evolutionary change. In order to shift average characteristics of a population over time, natural selection needs to be acting on that variation.
April 19, 2013 
Dennis Venema 
Genetics, History of Life 
36
 
Evolution Basics: The Basis of Heritable Variation, Part 1

Evolution Basics: The Basis of Heritable Variation, Part 1

Taken together, the properties of DNA match what we observe in nature: faithful reproduction of form, but not perfect reproduction of form. At its base, constancy and heritable variation in biological populations trace back to how DNA functions.
May 02, 2013 
Dennis Venema 
Genetics 
23
 
Evolution Basics: The Basis of Heritable Variation, Part 2

Evolution Basics: The Basis of Heritable Variation, Part 2

Taken together, these mechanisms introduce variation into populations, and since that variation is in DNA, the variation is heritable. Variation at the chromosome level may influence the function of genes, and ultimately traits at the level of the organism.
May 03, 2013 
Dennis Venema 
Genetics 
11
 
Evolution Basics: From Variation to Speciation, Part 1

Evolution Basics: From Variation to Speciation, Part 1

…in small populations, drift can have a large impact on allele frequencies from one generation to the next. In large populations, natural selection predominates, and drift has little impact. Both of these mechanisms can contribute to changing allele frequencies over time within populations, and as such both can be factors that contribute to speciation events.
May 16, 2013 
Dennis Venema 
Genetics 
28
 
Evolution Basics: From Variation to Speciation, Part 2

Evolution Basics: From Variation to Speciation, Part 2

Once separated from the larger population, the smaller “founding” group no longer received new alleles from it, nor passed new alleles that arose back to it. Despite being two populations of the same species, they were now genetically sealed off from one another, and differences in allele frequencies began to accrue between them.
May 17, 2013 
Dennis Venema 
Genetics 
273
 
Evolution Basics: From Variation to Speciation, Part 3

Evolution Basics: From Variation to Speciation, Part 3

Once populations become spread out over a wide geographic area, the differences between the populations at the extremities (populations A and E in our diagram) can become quite significant. In some cases, interestingly enough, the populations on the ends of the string can be different enough that they do not recognize each other as members of the same species, despite the fact that they are genetically connected through a series of intermediate populations.
May 30, 2013 
Dennis Venema 
Genetics, History of Life 
7
 
Evolution basics: From Variation to Speciation, Part 4

Evolution basics: From Variation to Speciation, Part 4

For those “early” flies that were attracted to this new, but somewhat similar fruit in their environment, the result would be twofold: (a) finding a food source with reduced competition from members of their own species, and (b) finding a mate with similar tendencies of attraction to apples. What was previously a “losing” genetic combination (hatching too early, without sufficient food or reasonable prospects for a mate) was now a “winning” combination.
May 31, 2013 
Dennis Venema 
Genetics 
33
 
Evolution Basics: Genomes as Ancient Texts, Part 1

Evolution Basics: Genomes as Ancient Texts, Part 1

…while errors made by human scribes tend preserve a meaning of some kind (even if it is an altered meaning), DNA replicating enzymes do not check to see if meaning (i.e. function) is preserved as they copy. (The functional check for a DNA sequence will come later as that particular organism develops (or not) and reproduces (or not). In other words, natural selection is the check for “meaning” for a DNA sequence).
June 13, 2013 
Dennis Venema 
Genetics 
1
 
Evolution Basics: Genomes as Ancient Texts, Part 2

Evolution Basics: Genomes as Ancient Texts, Part 2

… these observations indicate that there is no biological need for nearly identical genes at the amino acid level, or even at the DNA level, in different species. Numerous amino acid sequences, and even numerous DNA sequences, are equally capable of performing the same function. Yet, what we see time and again (across whole genomes!) are nearly identical genes, with a few (often shared) differences – exactly what speciation events would be expected to produce.
June 14, 2013 
Dennis Venema 
Genetics 
32
 
Evolution Basics: Genomes as Ancient Texts, Part 3

Evolution Basics: Genomes as Ancient Texts, Part 3

Taken together, what we observe when comparing the overall structure of the human genome to other primates is that (a) our genomes do indeed have the features one would predict them to have if they are copies of a shared ancestral genome, and (b) the differences we do observe are easily accounted for by well-known mechanisms. These observations strongly support the hypothesis that our species arose through an evolutionary process.
June 27, 2013 
Dennis Venema 
Genetics 
 
Evolution Basics: Genomes as Ancient Texts, Part 4

Evolution Basics: Genomes as Ancient Texts, Part 4

…as we have seen before, there is no biological need for these sequences to be this identical – in fact, even for this small region of this gene, there are over 53 million (!) different ways to code for the exact same amino acid sequence. Most of those sequences are much more different from the human sequence than the nearly identical sequences we observe in other primates.
June 28, 2013 
Dennis Venema 
Genetics 
7
 
Evolution Basics: Genomes as Ancient Texts, Part 5

Evolution Basics: Genomes as Ancient Texts, Part 5

The longer two species have a shared history, the more similar we expect their gene sequences to be. The longer they have had a separate history, the more different we expect their genes to be, due to mutation events occurring in the “separate history” portion of the phylogeny.
July 18, 2013 
Dennis Venema 
Genetics 
 
Evolution Basics: Species Trees, Gene Trees and Incomplete Lineage Sorting

Evolution Basics: Species Trees, Gene Trees and Incomplete Lineage Sorting

If a gene has variation in a population undergoing speciation events, it is expected that some of the time it will assort with a pattern that does not match the species pattern – in some cases, it will have a gene tree that is “discordant” with the species tree.
July 19, 2013 
Dennis Venema 
Genetics 
7
 
Evolution Basics: Incomplete Lineage Sorting and Ancestral Population Sizes

Evolution Basics: Incomplete Lineage Sorting and Ancestral Population Sizes

Discordant gene trees are a window to the past that reveal the genetic diversity of an ancestral population – how many alleles it maintained for a given region of the genome. By comparing large sets of genome data from humans, chimpanzees and gorillas, it is possible to get an accurate estimate of population size for the (H,G,C) ancestral population (about 50,000 individuals).
August 01, 2013 
Dennis Venema 
Genetics 
 
Evolution Basics: An Introduction to Homoplasy and Convergent Evolution

Evolution Basics: An Introduction to Homoplasy and Convergent Evolution

Homoplasies can be as simple as single DNA monomer changes (as in this example), or as complex as the independent reorganization of multiple systems with numerous genes and body parts to converge on a solution (as in the case for powered flight in birds and bats). In both cases, however, we can determine that they arose as independent events on separate lineages because these features do not fit onto the species tree as unique events.
August 02, 2013 
Dennis Venema 
Genetics, History of Life 
3
 
Evolution Basics: Convergent Evolution and Deep Homology

Evolution Basics: Convergent Evolution and Deep Homology

One common misconception I encounter about evolution is that it is predominantly a random process – one that is mainly influenced by chance events. While we have already shown that evolution has a strongly non-random component (natural selection), this discussion of convergent evolution further demonstrates that evolution is repeatable in certain important ways.
August 15, 2013 
Dennis Venema 
Genetics 
16
 
Evolution Basics: Coevolution and Predator / Prey “Arms Races”

Evolution Basics: Coevolution and Predator / Prey “Arms Races”

Moths that are merely using a warning sound to advertise their toxicity emit signals in a pattern that does not produce interference with bat echolocation, but Bertholdia emits ultrasonic bursts well suited for a “jamming” purpose. Recent work on these moths and their bat predators has teased apart a possible “warning” effect and a “jamming” effect by using bats familiar with the moths and actively pursuing them as prey.
August 16, 2013 
Dennis Venema 
Genetics 
3
 
Evolution Basics: Parasitism, Mutualism and Cospeciation

Evolution Basics: Parasitism, Mutualism and Cospeciation

Beyond the matching pattern of speciation, the divergence times for human and chimpanzee body lice agrees with the speciation times for their hosts. Human and chimpanzee body lice separated approximately 5.6 million years ago, which falls within the range of times estimated for the human / chimpanzee divergence…
August 29, 2013 
Dennis Venema 
Genetics 
1
 
Evolution Basics: Endosymbiosis and the Origins of Mitochondria and Chloroplasts

Evolution Basics: Endosymbiosis and the Origins of Mitochondria and Chloroplasts

The ability to use solar energy for energy conversion within the cell is obviously a great advantage to photosynthetic organisms. Interestingly, some animal lineages have developed quasi-endosymbiotic relationships that allow them to photosynthesize using captured chloroplasts. For example, various species of sea slugs are able to retain chloroplasts from the algae they feed on, distribute them within their own tissues, and thereafter use them for photosynthesis, freeing them from the need to ingest additional food for months at a time.
August 30, 2013 
Dennis Venema 
Genetics 
1
 
Evolution Basics: The Cambrian Diversification and Assembling Animal Body Plans, Part 1

Evolution Basics: The Cambrian Diversification and Assembling Animal Body Plans, Part 1

All living arthropods have a suite of defining characteristics such as a hard external skeleton (exoskeleton), specialized body segments, and specialized appendages. While these characteristics are useful for defining modern arthropods, these criteria become less useful as we travel back through the evolutionary history of arthropods.
September 12, 2013 
Dennis Venema 
Genetics, History of Life 
3
 
Evolution Basics: The Cambrian Diversification and Assembling Animal Body Plans, Part 2

Evolution Basics: The Cambrian Diversification and Assembling Animal Body Plans, Part 2

For better or for worse, taxonomy has been trying to shoehorn ancient species into modern categories. The fact that ancient species blur the distinctions between modern day taxonomic groups (such as arthropods and onychophorans) shows that what we recognize as large taxonomic groups (such as what we call “phyla”) are in fact best described as monophyletic groups in nested sets.
September 13, 2013 
Dennis Venema 
Genetics, History of Life 
14
 
Evolution Basics: Assembling Vertebrate Body Plans, Part 1

Evolution Basics: Assembling Vertebrate Body Plans, Part 1

…the probability that any given fossil species is a direct ancestor of a modern-day species is vanishingly small. Fossilization is a highly infrequent event – fossils spaced 10,000 or even 100,000 years apart would be considered to be nearly simultaneous in their timing from a geological perspective – and the chances of such an infrequent event preserving a direct ancestor is highly unlikely.
October 03, 2013 
Dennis Venema 
Genetics, History of Life 
24
 
Evolution Basics: Assembling Vertebrate Body Plans, Part 2

Evolution Basics: Assembling Vertebrate Body Plans, Part 2

These stem groups show us that the vertebrate body plan was assembled over time in a stepwise fashion, and that its “sudden appearance” in the Cambrian record is in fact not sudden at all, but rather the end result of a process that extends much deeper into the past.
October 04, 2013 
Dennis Venema 
Genetics, History of Life 
 
Evolution Basics: Assembling Vertebrate Body Plans, Part 3

Evolution Basics: Assembling Vertebrate Body Plans, Part 3

Eusthenopteron had articulated bones in its front lobe fins – bones we recognize in modern-day tetrapods as the humerus, radius, and ulna. These are the long bones that make up the forelimb in crown-group tetrapods – but in Eusthenopteron, these bones are short, and serve as the support for fins, not limbs (in the tetrapod sense).
October 10, 2013 
Dennis Venema 
Genetics, History of Life 
 
Evolution Basics: Assembling Vertebrate Body Plans, Part 4

Evolution Basics: Assembling Vertebrate Body Plans, Part 4

…despite decades of protests from antievolutionists that no possible intermediate forms for birds could exist, we see a group of fossil species that meets the criteria handily – and demonstrates that yes, there was a use for “partially-formed feathers and wings.”
October 24, 2013 
Dennis Venema 
Genetics, History of Life 
60
 
Evolution Basics: Assembling Vertebrate Body Plans, Part 5

Evolution Basics: Assembling Vertebrate Body Plans, Part 5

At the genetic level, genes required for yolk production would eventually no longer contribute to the survival or reproduction of the organism – meaning that they were no longer under selection, and now free to accumulate mutations without consequence to the organism.
November 07, 2013 
Dennis Venema 
Genetics, History of Life 
3
 
Evolution Basics: The Placental Revolution, Part 1

Evolution Basics: The Placental Revolution, Part 1

“The placental diversification in the Paleogene is highly interesting from an evolutionary standpoint since niches that were vacated by reptiles were in many cases filled by placental species – species that were shaped over time to fill those niches.”
November 21, 2013 
Dennis Venema 
Genetics, History of Life 
9
 
Evolution Basics: The Placental Revolution, Part 2

Evolution Basics: The Placental Revolution, Part 2

“One shared feature of haplorhine primates is their curious inability to make their own vitamin C, forcing them to acquire it from their diet. This is unusual – the majority of mammals (including non-haplorhine primates) are able to make vitamin C starting from the basic dietary sugar glucose.”
December 12, 2013 
Dennis Venema 
Genetics, History of Life 
 
Evolution Basics: From Primate to Human, Part 1

Evolution Basics: From Primate to Human, Part 1

For many years, it was unclear if humans were more closely related to chimpanzees or to gorillas, but full genome sequences allowed us to resolve the issue.
January 02, 2014 
Dennis Venema 
Genetics, History of Life 
3
 
Evolution Basics: From Primate to Human, Part 2

Evolution Basics: From Primate to Human, Part 2

The appreciation of the hominin group as a bushy tree rather than a ladder would elude scientists for some time, to say nothing of the general public.
January 23, 2014 
Dennis Venema 
History of Life, Human Origins 
 
Evolution Basics: From Primate to Human, Part 3

Evolution Basics: From Primate to Human, Part 3

The end for Piltdown would be swift in coming, and Le Gros Clark would be one of the key figures in unmasking Piltdown for what it was.
February 06, 2014 
Dennis Venema 
History of Life, Human Origins 
2
 
Evolution Basics: From Primate to Human, Part 4

Evolution Basics: From Primate to Human, Part 4

The diversity of [hominin] remains both complicates the details of our evolution – in that we cannot be absolutely certain which (if any) of these groups are directly ancestral to our own species – and clarifies the overall picture, since these are our close relatives even if not our direct ancestors.
February 27, 2014 
Dennis Venema 
Genetics, History of Life, Human Origins 
2
 
Evolution Basics: Becoming Human, Part 1: Mitochondrial Eve and Y Chromosome Adam

Evolution Basics: Becoming Human, Part 1: Mitochondrial Eve and Y Chromosome Adam

Wait just a second, you say – isn’t the evidence strong that modern humans descend from a population that has never numbered less than about 10,000 individuals (and as such, is a topic of significant theological consideration. How is it, then, that all humans can share a single woman and single man as common ancestors?
March 13, 2014 
Dennis Venema 
Adam, the Fall, and Sin, Genetics, History of Life, Human Origins 
9
 
Evolution Basics: Becoming Human, Part 2: Language Evolution and Lines on a Gradient

Evolution Basics: Becoming Human, Part 2: Language Evolution and Lines on a Gradient

Language evolution is in fact one of the better analogies for biological evolution, in that it forces one to think of change in the context of a population over time. Just as a language has a population of speakers, so too a species has a population of genomes.
May 22, 2014 
Dennis Venema 
Genetics, History of Life, Human Origins 
7
 
Evolution basics: Becoming human, Part 3: Paleogenomics and the tangled web of human speciation

Evolution basics: Becoming human, Part 3: Paleogenomics and the tangled web of human speciation

Amazingly as it sounds, in the proper conditions DNA can persist inside bones and teeth for tens (or even hundreds) of thousands of years. Given our interest in human evolution, DNA sequencing of Neanderthals was one of the first uses for this new technology – and for the first time we could test the hypothesis of interbreeding with genetic evidence.
June 05, 2014 
Dennis Venema 
Genetics, History of Life, Human Origins 
32
 
Evolution Basics: At the Frontiers of Evolution, Part 1: Frontier Science, Abiogenesis and Christian Apologetics

Evolution Basics: At the Frontiers of Evolution, Part 1: Frontier Science, Abiogenesis and Christian Apologetics

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 where the science is far from settled.
June 19, 2014 
Dennis Venema 
Creation & Origins, Genetics, History of Life, Science as Christian Calling 
56
 
Evolution Basics: At the Frontiers of Evolution, Part 2: Abiogenesis and the Question of Naturalism

Evolution Basics: At the Frontiers of Evolution, Part 2: Abiogenesis and the Question of Naturalism

But Dennis, you might say, aren’t you assuming that life had a “natural” origin? Aren’t you discounting the possibility that God might have brought life about through supernatural means? Haven’t you capitulated to “naturalism” from the outset?
July 10, 2014 
Dennis Venema 
Creation & Origins, History of Life, Science & Worldviews 
15
 
Evolution Basics: At the Frontiers of Evolution, Part 3: The RNA World Hypothesis

Evolution Basics: At the Frontiers of Evolution, Part 3: The RNA World Hypothesis

So, will science ever solve the problem of abiogenesis? Perhaps not – though when I reflect on the fact that we are only 400 years removed from the time of Galileo, I am reminded that many seemingly unsolvable scientific problems have indeed been solved. And along with Bonhoeffer, I delight in these scientific advances that give us an ever-larger picture of God and his faithfulness to his creation.
August 07, 2014 
Dennis Venema 
Genetics, History of Life 
4
 
Evolution Basics: At the Frontiers of Evolution, Part 4: Contingency vs. Convergence

Evolution Basics: At the Frontiers of Evolution, Part 4: Contingency vs. Convergence

Given that both contingency and convergence seem to be significant factors in evolutionary history, it is only natural for scientists to wonder which force has the upper hand. Is evolution primarily contingent, with convergence playing only a minor role? Or is evolution largely a convergent phenomenon, where contingent factors have little overall influence?
August 21, 2014 
Dennis Venema 
Evolution - How It Works, Randomness 
96
 
At the Frontiers of Evolution, Part 5: Contingency and Convergence in the LTEE

At the Frontiers of Evolution, Part 5: Contingency and Convergence in the LTEE

How twelve cultures of bacteria give evidence of the power of evolution.
September 04, 2014 
Dennis Venema 
Evolution - Evidence, Evolution - How It Works, Randomness 
2
 
Evolution Basics: Evolution and the Christian, Part 1:  Is Evolution a Purposeless Mechanism?

Evolution Basics: Evolution and the Christian, Part 1:  Is Evolution a Purposeless Mechanism?

One of the primary concerns about evolution that I encounter is the question of “randomness” – by which most folks mean something to the effect that evolution is an unpredictable, uncontrolled process – that as such could not be used by God as a purposeful mechanism to bring about his aims.
September 18, 2014 
Dennis Venema 
Divine Action & Purpose, Evolution - How It Works, Randomness 
189
 
Evolution and the Christian, part 2: Fearfully and Wonderfully Made

Evolution and the Christian, part 2: Fearfully and Wonderfully Made

Some of the Christian objections to evolutionary creation come from a misunderstanding of what the Bible means when it says “God created”.
October 16, 2014 
Dennis Venema 
Ancient Cultures, Biblical Authority, Biblical Interpretation, Divine Action & Purpose 
9
 
Evolution and the Christian, Part 3: Speaking the Truth in Love

Evolution and the Christian, Part 3: Speaking the Truth in Love

There is a need to speak out truthfully about evolution, but love and a desire for Christian unity must be foremost when doing so.
October 17, 2014 
Dennis Venema 
Biblical Authority, Christian Unity 
44