What Organisms Populated Land First?

Life on Earth originated in the ocean, but what was the first group of organisms to move onto the land? When thinking about life moving to land, many people imagine the classic image of a primitive fish species evolving legs and crawling onto a beach. Although that is more or less how vertebrates first made the transition to terrestrial life, there were already many other organisms thriving on land by the time they got there.

Although it’s difficult to determine for certain from fossils alone, most scientists believe that the first organisms to take to the land were freshwater plants. These plants originally inundated swamps and wetlands, before eventually evolving into fully terrestrial plants that could live and reproduce away from the water.

Early terrestrial plants had to overcome several obstacles to adapt to their new lifestyle. These included being able to hold themselves upright without support from the water, and withstanding more intense levels of sunlight. These new adaptations allowed them to take advantage of otherwise unclaimed habitat.

Once the first land plants had established habitat and food, the first animals to move to land were early arthropods. These included the forbearers of myriapods (millipedes and centipedes), arachnids (spiders and scorpions), and insects. Arthropods had been living on land of thousands of years before vertebrates came on the scene.

The first vertebrates to move to land were primitive fish, probably resembling lungfish or mudskippers, which eventually evolved into the fist amphibians. Adaptations like breathing air and legs to move on land allowed them to take advantage of the terrestrial prey and habitat created by plants and arthropods.