Physical Obstacles to Transition from Water to Land

The claim that fish are the ancestors of land-dwelling creatures is invalidated by anatomical and physiological observations as much as by the fossil record. When we examine the huge anatomical and physiological differences between water- and land-dwelling creatures, we can see that these differences could not have disappeared in an evolutionary process with gradual changes based on chance. We can list the most evident of these differences as follows

1- Weight-bearing: Sea-dwelling creatures have no problem in bearing their own weight in the sea, although the structures of their bodies are not made for such a task on land. However, most land-dwelling creatures consume 40 percent of their energy just in carrying their bodies around. Creatures making the transition from water to land would at the same time have had to develop new muscular and skeletal systems to meet this energy need, and this could not have come about by chance mutations.

The basic reason why evolutionists imagine the coelacanth and similar fish to be the ancestors of land-dwelling creatures is that their fins contain bones. It is assumed that over time these fins turned into load-bearing feet. However, there is a fundamental difference between these fish's bones and land-dwelling creatures' feet. It is impossible for the former to take on a load-bearing function, as they are not linked to the backbone. Land-dwelling creatures' bones, in contrast, are directly connected to the backbone. For this reason, the claim that these fins slowly developed into feet is unfounded.

2- Heat retention: On land, the temperature can change quickly, and fluctuates over a wide range. Land-dwelling creatures possess a physical mechanism that can withstand such great temperature changes. However, in the sea, the temperature changes slowly, and within a narrower range. A living organism with a body system regulated according to the constant temperature of the sea would need to acquire a protective system to ensure minimum harm from the temperature changes on land. It is preposterous to claim that fish acquired such a system by random mutations as soon as they stepped onto land.

3- Water: Essential to metabolism, water needs to be used economically due to its relative scarcity on land. For instance, the skin has to be able to permit a certain amount of water loss, while also preventing excessive evaporation. That is why land-dwelling creatures experience thirst, something that sea-dwelling creatures do not do. For this reason, the skin of sea-dwelling animals is not suitable for a nonaquatic habitat.

4- Kidneys: Sea-dwelling organisms discharge waste materials, especially ammonia, by means of their aquatic environment: In freshwater fish, most of the nitrogenous wastes (including large amounts of ammonia, NH3) leave by diffusion out of the gills. The kidney is mostly a device for maintaining water balance in the animal, rather than an organ of excretion. Marine fish have two types. Sharks, skates, and rays may carry very high levels of urea in their blood. Shark's blood may contain 2.5% urea in contrast to the 0.01-0.03% in other vertebrates. The other type, i. e., marine bony fish, are much different. They lose water continuously but replace it by drinking seawater and then desalting it. They rely more on tubular secretion for eliminating excess or waste solutes.

Each of these different excretory systems is very different from those of terrestrial vertebrates. Therefore, in order for the passage from water to land to have occurred, living things without a kidney would have had to develop a kidney system all at once.

5- Respiratory system: Fish "breathe" by taking in oxygen dissolved in water that they pass through their gills. They cannot live more than a few minutes out of water. In order to survive on land, they would have to acquire a perfect lung system all of a sudden.

It is most certainly impossible that all these dramatic physiological changes could have happened in the same organism at the same time, and all by chance.