Why Macroevolution Doesn’t Have Enough Time: A simple look at Haldane’s Dilemma and the real limits of evolution

Imagine someone tells you that a whole library was rewritten by hand in one weekend. Not copied by machines or scanned, but written line by line, carefully checked, with no mistakes. Would you believe it? Or would you start wondering if there was even enough time for that to happen? That question about time is exactly the kind of problem we face when we talk about macroevolution.

Before going any further, it helps to define two terms. Microevolution refers to small changes within a kind, such as differences in size, color, or resistance to disease. Macroevolution refers to large-scale change, in which entirely new kinds of organisms, organs, and body plans are supposed to appear over time. The debate is not about microevolution. The debate is about whether macroevolution is even possible within the available time.

Macroevolution is not just the idea that small changes happen in living things. We can all see that they do. The real claim is much bigger. It says that huge, complex changes happened fast enough to turn simple life into complex life, and to turn ape-like creatures into humans. So, the real question is not whether DNA can change. The real question is whether enough helpful, function-building changes can happen and spread fast enough to build entirely new living systems.

This is where Haldane’s dilemma becomes important. J.B.S. Haldane was an evolutionary biologist, but he noticed a serious problem. Even good mutations don’t spread instantly; they have to move through a whole population, generation by generation, and that takes time. For a new trait to replace an old one, the individuals with that trait must survive and reproduce more than others. That means some individuals must fail so others can succeed. This process has a real cost, and populations can only afford that cost so many times.

A simple way to picture this is to think about a single-lane road. You can have a thousand cars waiting to pass through, but only so many can go through each hour. No matter how many cars you add, the road itself stays narrow. Natural selection works the same way. No matter how many mutations exist, only a limited number can become permanent in a population over time. That speed limit is the heart of Haldane’s dilemma.

Haldane calculated that in a standard population, it takes roughly 300 generations for a single helpful trait to become fixed across the whole group. If humans and ape-like creatures were separated 6 million years ago, that only leaves enough time for a few thousand beneficial mutations. However, to transform an ape-like creature into a human would require millions of specific genetic changes. The math simply doesn't add up.

Some people respond by saying that sexual reproduction and recombination solve this problem. It is true that sex mixes genes and creates new combinations, but mixing is not the same as building. The real problem is not how many changes exist, but how many useful changes can spread and become fixed. Most rapid examples of microevolution involve small adjustments, such as changes in size, color, or resistance to disease. Sometimes they even involve loss of function that helps in a special environment, but macroevolution requires something much bigger. It requires new systems to be built.

Would you expect a few software updates on your phone to slowly turn it into a spaceship? Real living things are tightly connected systems. One change often affects many parts at once. Many changes involve trade-offs, in which gaining one benefit entails a loss somewhere else. So even if recombination helps in some cases, it doesn’t remove the basic speed limit that selection operates under.

At this point, two common objections often arise. The first is that most genetic changes are neutral, meaning they don’t affect survival. That is true, but neutral changes don’t build new organs or new body plans. They add background noise to the system, not a new structure.

 Some argue that 'neutral' mutations (changes that neither help nor harm) occur constantly, providing a pool of genetic variation, but waiting for neutral changes to accidentally form a complex, working machine is like waiting for the wind to assemble a functioning engine out of loose parts. Without the guiding hand of natural selection to 'lock in' progress, random changes destroy information faster than they create it.

The second objection is that large populations make evolution easy. Large populations can produce more mutations, but they don’t remove the main limit. Selection still works through survival and reproduction, and that process still has a narrow pathway.

So, the time problem remains. Haldane’s dilemma doesn’t say evolution is impossible; it says there is a limit to how many useful, function-building changes can spread in a population over time. In large animals, the main limit is not mutation, but fixation. Each useful change has a real cost, and building a complex life would require many such changes. In simple terms, evolution is not limited by ideas, but by math.

Another way to think about fixation is like replacing a faulty part in every car in a large taxi fleet. You might design a better engine today, but you cannot instantly replace it in every vehicle. Each old car has to break down or be retired, and each new car has to be built with the new engine. That replacement happens one vehicle at a time. The size of the fleet limits how fast the upgrade can spread.

In biology, individuals cannot be upgraded. They must be replaced through birth and death. That makes the process inherently slow.

When we look at the fossil record, we often see long periods where life stays mostly the same. That doesn’t mean nothing changes at all. It means that big structural changes seem rare. If complex life were being built slowly and steadily, we might expect smooth, continuous transitions. Instead, we see long stretches of stability, followed by relatively sudden appearances of new forms. That pattern suggests strong limits, not endless flexibility.

Mutations themselves also raise a problem. Mutations are random changes to systems that already work. In complex systems, random changes usually cause problems rather than improvements. Yes, some mutations help in specific situations, but macroevolution requires many coordinated changes that work together without breaking the system at any step. Imagine throwing random letters onto a page. Over time, you might get a few real words, but writing a full book that way is extremely unlikely. Random changes don’t easily build meaningful systems.

However, Haldane’s Dilemma isn't the only time problem. Even if evolution had infinite time to modify life, it still cannot explain how life began, which is why we need to ask a deeper question. Where did life come from in the first place? In everything we observe, life comes from life. The idea that life arose from non-life is called abiogenesis, but no one has shown a clear natural process for creating a working cell from scratch. A living cell is not just a pile of chemicals; it is an information system with instructions, error checking, and machines working together. The real question is not whether chemicals can exist, but what natural process can build coded systems from nothing. That gap is still wide.

So what makes the most sense? If blind chance and a limited selection process struggle to explain the complexity of life, what does? The Bible gives a simple answer. “I am fearfully and wonderfully made” (Psalm 139:14). “The things that are made show God’s power” (Romans 1:20). Science doesn’t destroy faith. When we take the limits of selection and the complexity of living systems seriously, it often points back to it.

Small changes and adaptations are real, but the leap from a simple life to a complex one requires more than time. It needs a process that can build real systems without constantly breaking them. So, the honest question remains, if not blind evolution, then what? The answer has been there from the beginning. “In the beginning God created the heavens and the earth” (Genesis 1:1). If complex systems can’t build themselves, maybe it’s time we stop asking how we got here by chance and start asking why we were made with such care.    

Souces

Haldane, J. B. S. “The Cost of Natural Selection.” Journal of Genetics, vol. 55, no. 3, 1957, pp. 511–524. doi:10.1007/BF02984069.

Sanford, John C. Genetic Entropy and the Mystery of the Genome. 4th ed., FMS Publications, 2014.

ReMine, Walter J. The Biotic Message: Evolution Versus Message Theory. St. Paul Science, 1993.

Behe, Michael J. Darwin’s Black Box: The Biochemical Challenge to Evolution. Free Press, 2006.

Behe, Michael J. The Edge of Evolution: The Search for the Limits of Darwinism. Free Press, 2007.

Lönnig, Wolf-Ekkehard. “Dynamic Genomes, Morphological Stasis, and the Origin of Irreducible Complexity.” Progress in Complexity, Information, and Design, vol. 3, no. 2, 2004, www.discovery.org/a/994.

Crow, James F. “The High Spontaneous Mutation Rate: Is It a Health Risk?” Proceedings of the National Academy of Sciences, vol. 94, no. 16, 1997, pp. 8380–8386. doi:10.1073/pnas.94.16.8380.