Creation Ministries International recently published an article titled “Autumn Leaves: Fall by Design” that walks readers through the fascinating biochemistry of leaf abscission—the process by which deciduous trees shed their leaves each fall. As a biologist, I found much of the article’s description of the abscission zone, the senescence sequence, and the cascade of chemical signals to be a perfectly reasonable summary of well-known plant physiology. The science, as far as it goes, is fine. It’s the conclusion tacked on at the end that runs into trouble.
The article’s closing argument is this: because leaf abscission involves a sequential genetic cascade—each step dependent on the one before it—the process is “all-or-nothing” and therefore could not have evolved step by step. The author explicitly compares it to other supposed examples of irreducible complexity, like the blood clotting cascade, and concludes that this system must have been designed by God to “fit the seasons He made.”
Let’s take that argument seriously and see where it leads.
What Were Seasons For in the Original Creation?
The first question that arises is one that young-earth creationists rarely address directly: what role did seasons play in the original “very good” creation? The CMI article confidently states that God designed deciduous trees “to fit the seasons He made,” citing Genesis 1:14 and 8:22. But think about what this claim requires. The entire purpose of deciduousness is to survive conditions that would otherwise kill the tree—harsh winters with freezing temperatures, reduced sunlight, and desiccating winds. The article itself emphasizes that “even a single frost or night of freezing air temperatures can quickly damage the living tissues in leaves and petioles.” Leaf-shedding is, at its core, a survival strategy for coping with a hostile environment.
So were there harsh, freezing winters in the original creation? Were there climates so punishing that trees needed an elaborate self-preservation system to avoid being killed by frost? Young-earth creationists have generally been reluctant to discuss the details of pre-Fall climate, and for good reason. Most YEC models envision the original creation as a world without the kinds of extreme weather and harsh conditions that characterize our present world. Many have proposed some form of global mild climate—a world without ice caps, without deserts, without the brutal winters that make deciduousness necessary.
If that’s the case, then who exactly needed this supposedly irreducibly complex system? If there were no killing frosts in the pre-Fall world, deciduous trees would have been shedding their leaves for no reason at all—throwing away perfectly functional photosynthetic organs in preparation for a winter that never came. That’s not good design. That’s waste. On the other hand, if you argue that there were harsh winters in the original creation, you’ve introduced a world of difficulty and environmental challenge that sits uneasily with the YEC vision of a “perfect” pre-Fall paradise.
This is the kind of question that sounds simple but turns out to be remarkably difficult for young-earth creationists to answer consistently. Either the pre-Fall world had deadly winters and needed deciduous trees, or it didn’t and the whole system was purposeless until after the Fall. Neither option is comfortable.
The Problem of Deciduous and Evergreen Species Within the Same “Kind”
But the deeper problem with the CMI article’s irreducible complexity argument lies in a pattern that the author apparently didn’t consider—or perhaps chose not to mention. If the genetic cascade controlling leaf abscission is truly an all-or-nothing system that could not have evolved, then every deciduous species should have inherited it directly from creation. It should be a fixed feature of certain created “kinds,” cleanly separating them from evergreen “kinds.”
But that’s not what we find in nature. Not even close.
Consider the oak genus Quercus. This is a group that most young-earth creationists would consider a single created “kind” or at most a few closely related kinds. And yet within this single genus we find both deciduous species, like the familiar red and white oaks of the eastern United States, and evergreen species, like the live oaks of the American South and the holm oak of the Mediterranean. If leaf abscission is an irreducibly complex, all-or-nothing system, how did some members of the oak “kind” end up with it and others without it? Within the young-earth framework, all these oaks descended from the same original created population after the Flood. That means either the deciduous machinery evolved in some oak lineages, or it was lost in others. Either way, the system is clearly not “all-or-nothing” in the way the article claims—it can be gained or lost, which is precisely the kind of modular, evolvable trait that the article says cannot exist.
And oaks are far from the only example. The genus Magnolia includes classic deciduous species in northern climates alongside the evergreen Southern magnolia. The genus Prunus—the cherries, plums, and peaches—includes deciduous fruit trees alongside evergreen species like the cherry laurel. Rhododendrons include both evergreen and deciduous species. The genus Vaccinium contains the evergreen huckleberry and the deciduous red huckleberry. Crape myrtles (Lagerstroemia) include both evergreen and deciduous species among their more than 50 members.
The pattern extends to the family level as well. The Rose family (Rosaceae) contains deciduous fruit trees alongside evergreen shrubs like Cotoneaster. The Laurel family (Lauraceae) includes the evergreen avocado and the deciduous sassafras. The Beech family (Fagaceae) contains the deciduous beeches alongside evergreen oaks. And perhaps most striking of all, the Cypress family (Cupressaceae)—a conifer family that is overwhelmingly evergreen—includes the famously deciduous bald cypress and dawn redwood. If the genetic cascade controlling leaf abscission cannot evolve in a step-by-step fashion, how do we account for deciduous conifers nested within a family that is otherwise evergreen?
What This Pattern Tells Us
This distribution of deciduous and evergreen strategies across plant families and genera is not some obscure corner of botany. It is one of the most well-documented patterns in plant ecology, and it tells us something important: the transition between evergreen and deciduous life history strategies has occurred repeatedly across the plant kingdom. It has happened independently in flowering plants and conifers, in tropical families and temperate ones, in trees and shrubs. The genetic and developmental toolkit for leaf senescence and abscission is not a monolithic, irreducible block. It is a modular system—one whose components can be up-regulated or down-regulated, activated or silenced, over evolutionary time.
This shouldn’t be surprising. The individual components of the abscission cascade—hormonal signaling, programmed cell death, enzymatic digestion of cell walls, nutrient resorption—are all processes that plants use for many other purposes. Ethylene signaling, for example, is involved in fruit ripening, flower senescence, and responses to wounding and pathogen attack. Programmed cell death is involved in the formation of xylem vessels. Cell wall degradation occurs during fruit ripening and seed dispersal. The abscission cascade is not a system built from scratch with unique, purpose-built components. It is an elegant redeployment and coordination of existing biochemical machinery—exactly the kind of system that can and does evolve through modification of existing regulatory networks.
The CMI article even hints at this, noting in a footnote that the abscission process described applies “not just to autumn leaves, but also petals, flowers, ripening fruits, and other dead or diseased parts.” This is precisely the point. The same basic machinery is used across many different plant organs and functions, which is strong evidence that its components have a broader evolutionary history and were not designed as a single indivisible package for one specific purpose.
A Familiar Pattern in Creationist Argumentation
This article follows a pattern I’ve encountered many times in creationist literature. A genuinely interesting biological system is described accurately and in some detail—enough to impress a general audience with its complexity. Then a design inference is attached to the description, usually involving words like “all-or-nothing,” “irreducibly complex,” or “carefully coordinated.” The implicit argument is that complexity equals impossibility of evolution. But the argument works only if you don’t look too broadly at the rest of the biological world, where related organisms frequently have and lack the trait in question, and where the individual components of the “irreducible” system turn out to serve other functions in other contexts.
I would argue that the autumn leaf is indeed a remarkable display of coordinated biological engineering. As a biologist, I find the process of senescence, nutrient resorption, and abscission to be one of the more elegant examples of how plants manage resources in a seasonal environment. But recognizing its elegance is not the same as claiming it could not have evolved. The evidence from comparative botany—the repeated, independent transitions between deciduous and evergreen strategies within the same families, genera, and even closely related species—tells us that this is precisely the kind of system that can be assembled, modified, and disassembled by natural processes over time.
As Christians who care about both truth and the integrity of our witness, we should be cautious about deploying scientific arguments that don’t hold up under scrutiny. The beauty of autumn leaves does not need a flawed design argument to point us toward the Creator. The heavens declare the glory of God whether or not any particular biochemical cascade meets the technical definition of irreducible complexity. And our theology is better served when we let the creation speak for itself, rather than forcing it into categories it doesn’t fit.
Blessings,
Joel
Naturalis Historia 
Comments or Questions?