The process of metamorphosis is a unique life cycle that poses a significant obstacle to evolutionary theory. Yet it is not frequently discussed in either creationist or evolutionary circles. This article is an attempt to stir up more discussion and thought about the topic. It will explore what metamorphosis is, how it works, and why it matters in the context of origins.
In order to understand metamorphosis, we must first have a definition of what we are talking about. Merriam-Webster.com defines metamorphosis as “a typically marked and more or less abrupt developmental change in the form or structure of an animal (such as a butterfly or a frog) occurring subsequent to birth or hatching.” That definition can be paraphrased into meaning a distinct change from the form an organism is born into, to the form it takes as an adult. This change occurs in fish, amphibians and most famously in insects. In each case, there is a vast change in form from newly hatched or born creature, to a fully functional adult.
Insect metamorphosis is perhaps the most well known type of metamorphosis. It is split into two types, complete and incomplete. Complete metamorphosis has four steps whereas incomplete has three. Complete metamorphosis begins when an adult insect lays eggs. Butterflies will be our example since they undergo complete metamorphosis. When the butterfly egg hatches, a larva stage emerges, known as the caterpillar. The caterpillars entire purpose is to eat. It does this very well, often consuming multiple times its own weight in food every day. Once it has grown to a certain size, which differs in every insect, it will undergo a dramatic change. From the larval stage, the caterpillar passes into the pupa stage. It does this by forming a hard, protective shell around its body. Once this shell has formed, the larva curls into a ball and essentially liquefies itself into a soup of complex chemicals. These chemicals undergo a massive transformation process. This process changes the insect from the larval to the adult stage. In the example of the butterfly, the larva passes through the pupa stage to get to the beautiful work of art we know as an adult butterfly. The adult is a completely recognizable adult insect, with all the necessary body parts.
Some insects do not undergo complete metamorphosis. Instead they undergo a modified process referred to as incomplete metamorphosis. Grasshoppers are a commonly seen example of an insect that undergoes incomplete metamorphosis. The adult grasshopper lays eggs. When these eggs hatch, a small growing form of grasshopper emerges called the nymph. This stage closely resembles their adult counterpart but often lacks wings or another such feature. The nymph stage is the stage that grows. They eat voraciously during this stage in order to increase in size rapidly. Eventually the nymph will graduate into the adult stage and the cycle will begin anew.
Fish also undergo metamorphosis but the process is vastly different than that of an insect. Fish metamorphosis takes place entirely within the egg itself. For bony fish, when the eggs are laid, there is very little inside. However, when the egg is fertilized, the organs and eyes begin to develop. The eyes develop as eyespots. Proper eyes do not form until after the embryo hatches into a larva. The embryo also develops a tail in the egg. The tail will be used to break open the egg when it is time to hatch. Upon hatching, most larva will feed off a yolk sac attached to their lower body. They will depend on this sac for two to four days, depending on water temperature, while their jaws and eyes form. Once these have formed, the newly hatched larva will resemble miniature adults and will be left to their own devices when it comes to finding food to eat.
Amphibians also undergo metamorphosis. The classic example of amphibian metamorphosis is the frog. Female frogs lay eggs which are fertilized externally. These egg masses hatch into tadpoles. These tadpoles barely resemble fully grown adults. They have external gills and a lengthy tail. Tadpoles go through multiple stages as they fill out into an adult frog. The gills are reabsorbed and the gill slits closed as the young frog develops lungs. The tail is also reabsorbed as the frog grows until it either disappears or is nearly unnoticeable in the adult. During this process the frog will begin to grow legs. The rear legs will appear first, while the tail is still existent. The front legs will begin to appear around the same time the tail is nearly absorbed. This entire process is under the control of the frogs thyroid gland.
The common thread of all these types of metamorphosis is the change an organism undergoes to develop into an adult. Evolutionists claim that this is evidence for their theory. They claim that if metamorphosis were to be halted part way through, such as it might be in the frog by turning off the thyroid gland, the resulting organism would be a new kind of organism and thus be proof of evolution. However this rests on a false premise. Even if this occurred, it would need to happen to organisms that were sexually mature. Even assuming it did, it would still have to happen twice in the same generation of the same population to an individual of each gender or the mutation would not be passed on. However, even the odds of the organism surviving such a mutation are low. If this is true, evolutionists should do a study in which they remove the thyroid hormone from tadpoles at a certain stage of development and see what the mortality rate is and if they are sexually mature at that point. Since sexual maturity is only found in adult frogs, this experiment is foredoomed to failure.
Metamorphosis is a stunning declaration of God’s design in nature. Design is necessary for a butterfly to somehow rearrange itself from a chemical soup. Design is needed for frogs to lose their gills and gain lungs. Those things do not happen without a plan, a design in place which permits them. No chance process would create such a change in life cycle. Such a process is blind to the future benefits of a fully developed adult insect and only sees the energy cost associated with getting there. Metamorphosis would have been selected against on that basis alone. Creationists have no problem with metamorphosis because a wise Master Designer hardwired it to work from the beginning. It had no need to develop gradually over time. It existed exactly as it is now from the beginning.