New Creation
[Originally published as the second section of The Novel Traits Conundrum]
By Jake Ramgren
Let’s take a look at biology
The idea that new genetic information can lead to new beneficial traits in an organism is not the same claim as the evolution of all organisms from one universal ancestor. While there is a lot of evidence that organisms have genetic potential to adapt to new environments (as creationists have consistently predicted) there is also an abundance of evidence that organisms sometimes gain genetic information in order to adapt.
Here, we will take a brief tour through the animal kingdom, beginning with the “lower animals” and working our way up the ladder of life.
Swimming Upstream
In the insect world, there is a textbook example of mutations causing new genes which, in turn, spread through a population via natural selection.
Introducing: the water strider.
Famous for its ability to stay on top of the water without breaking the surface tension, the water strider is an insect family with a shockingly rich number of species and genera. One of these genera (which includes 200 species), is notable for having fan-shaped extensions of their middle legs. One study proposes that these fans are the result of mutations creating a new feature in the insects.
Why do the researchers think these fans were the result of mutation? To answer this, we need to look at the genetics. What researchers observed were two water strider genes that were clearly duplicates. One of these duplicates contained clear genetic markers indicating mutation had occurred. This duplicated gene, which the scientists named “geisha,” was controlling the expression of the leg fans!
What does this mean? Well, sometimes mutations can cause a gene to be copied so there are two identical versions of the same gene. Initially, the copy has no function, because the original gene still performs its task and there is no need for two genes to do the same thing. But if the copy undergoes more mutations, it can develop a new function that is beneficial to the organism. In this case, the duplicated gene’s new function was creating new wing fans!
These dramatic fans gave the striders the ability to move against water currents. Genus Rhagovelia has the geisha gene (and therefore leg fans), while genus Stridulivelia does not.
These new leg fans helped the striders swim upstream against a current, allowing them to access new resources and environments that were unavailable before. It is a clear example of a beneficial trait appearing because of the input of new genetic information!
A New Kind of Arms Race
Have you ever heard of an “arms race”? In the world of humans, this refers to a race between two or more parties to attain weapons to gain an advantage in a conflict. In biology, an arms race refers to competition between predators and their prey. Both species are desperate to adapt quickly in order to survive. The “weapons” in this analogy are positive biological traits that allow a species to overcome the competition. One such arms race exists between garter snakes (the predator) and newts (the prey).
In this case, the newt species is adapting towards increased toxicity to escape the snakes, while the garter snake is continually developing immunity to the newt poison, allowing them to consume more prey. The newt’s toxin, called tetrodotoxin (TTX), causes paralysis and death to creatures that eat them. The exception to this rule is garter snakes, which have varying degrees of immunity and therefore varying degrees of susceptibility to the toxin.
This all seems fair and square, except the garter snake has a special trick. While the arms race has pressured garter snakes and newts to increase immunity and toxicity respectively, garter snakes that live closely with newts have developed a new genetic trait that gives them complete immunity to the newt toxins. Once again, this was not an adaptation obtained from genes already present in the organism. This was new genetic code that prevented TTX from binding to the snake’s proteins. Without being able to bind, the newt toxin could no longer cause paralysis and death in their predators. In this case, mutations substituted entire amino acids from the binding site, which in turn gave certain snake lineages complete immunity to newt toxins.
Is This Really New?
We know this was a derived trait and not one that was already present in the species and simply turned on or off as creationists might suspect. Why? Because populations of snakes that encounter less newts have less immunity.
Some studies focused on the snake-newt arms race have found that snakes with immunity are slower than those with less immunity, meaning that immunity has a “trade-off.” It is therefore quite possible that garter snakes eventually branch into two distinct populations: immune but slow populations that live near newts, and faster but non-immune snakes that are more at risk of predation than newt toxin.
In other words, immunity to TTX is a genetically based trait that arose independently in some lineages, but not others, based on their proximity to the poisonous newt populations. It was not a feature that was present in the ancestral garter snake before these garter snake lineages diverged.
Already, these examples seem to indicate that, generally speaking, new genetic traits can arise through mutation and spread in response to pressures in the environment. But let’s keep going up the chain of being.
Are there any examples of new traits arising in mammals?
I Can Digest That… Now
Let’s take a closer look at the primates. Rhesus monkeys typically only digest leafy plant material. This is unusual for primates. Most kinds eat fruit or insects. In fact, mammals typically cannot digest cellulose, so these monkeys (like cows) have symbiotic bacteria in their stomach to digest the leaves for them. Their pancreas then secretes enzymes called RNase which break down the bacteria in the small intestine so their bodies can reuse the nitrogen from the plants.
The gene that produces RNase (creatively named RNASE1) is not unique to rhesus monkeys. All leaf-eating monkeys (subfamily “colobines”) have this gene, as do humans. But in the rhesus monkey, a random duplication event created a sister gene, dubbed RNASE2. After undergoing several mutations of its own, RNASE2 is now quite unique, and differs from the original gene by nine amino acids. It also has a novel function.
It turns out, RNASE2 allows rhesus monkeys to digest that bacterial RNA at a lower pH level (6.3) than the original gene RNASE1 (7.4). This lower pH level has been shown experimentally to be six times more efficient for RNA digestion! So, in summary, a gene duplicate underwent several mutations which caused rhesus monkeys to digest their food far more effectively.
Gene Duplications: Difficult to Digest?
Similar to the water striders, this new feature of the rhesus monkeys arose through a novel gene that did not exist previously. In this case, the gene was a duplication. It was useless for a time before mutations changed the gene and gave it a new function. In turn, this novel innovation allowed the organism to adapt to new environments and access new resources. Such a mechanism is so efficient that some evolutionary biologists believe gene duplication is the primary mechanism by which new genes arise and organisms evolve.
In all likelihood, RNASE2 was not a gene that was present in the originally created monkey kind. It arose through a combination of gene duplication and beneficial mutations, in response to environmental or selective pressure. This does not mean the entire theory of evolution is proven true. It just means creationists should adopt the appearance of new traits and new genes into their biological models, because we can observe it happening in real time.
Got Lactase-phlorizin Hydrolase?
If you are getting tired of this tour through the natural world, fear not. I saved the best for last. It turns out, we humans are not without our genetic adaptations. In perhaps the most famous of these beneficial mutations, humans evolved a new genetic ability: to digest milk!
People digest food with special proteins called enzymes. All proteins are made and regulated by genes. The enzyme that digests lactose, in humans, is called lactase-phlorizin hydrolase (LPH). In mammals, this enzyme is only produced during early development when offspring is weaning. LPH has different regions which break down different substances. Lactase is the part of the enzyme responsible for digesting lactose.
In lactose intolerant people, LPH activity rapidly declines after the weaning stage (around 2 years of age). In fact, this is how it is for most mammals, and humans used to be no exception. It was a small but dramatic turn of events that led to lactose digestion in human adults. Several random mutations near the lactase gene caused some humans to produce LPH past the weaning stage and into adulthood, and this newfound trait is now called “lactase persistence” (LP).
Map from Beja-Pereira et al. (2003) showing a connection between cattle breeding and human lactose persistence (LP). The graph labeled “b” shows density of genetic diversity (orange) in neolithic dairy cattle. The “c” graph shows density of the LP gene among humans in the present (also in orange).
How Lactase Persistence Crossed Continents
Now, not everyone has the LP trait. The mutation spread through only some populations of humans. Which ones? Well, it was by observing maps of LP that led scientists to explore the genetic features behind the trait. They noticed that only the descendants of dairy breeding populations could digest lactose as adults.
Human populations that do not breed dairy would get no selective advantage from LP, and therefore the trait did not catch on. When a genetic trait spreads quickly through a population because it is biologically advantageous, biologists refer to it as a “selective sweep.” The fact that LP not only arose by mutation but also swept through a population makes it an observable example of adaptation at work. Every time you drink milk, then, you are utilizing random mutations that gave your ancestors a novel genetic trait!
Hopefully it is now clear that novel genetic information can introduce new beneficial traits to a population. The question now posed to creationists is: what does this mean for young age creationism?
Footnotes
- Zhang, R., & Gray, P. M. (2017). Evolutionary GEM: The Evolutionary Arms Race of Garter Snakes and Newts. Western Undergraduate Research Journal: Health and Natural Sciences, 8(1).
Zhang, J., Zhang, Y., & Rosenberg, H.F. (2002). Adaptive evolution of a duplicated pancreatic ribonuclease gene in a leaf-eating monkey. Nature Genetics, 30, 411-415.
