If humans were not the dominant species on Earth, the dominant species would depend on various factors, including the ecological niche, environmental conditions, and the specific time frame considered. Earth's history has seen the rise and fall of numerous dominant species, each of which held prominence for different periods.
Throughout geological history, there have been times when various species dominated the planet:
Dinosaurs: During the Mesozoic Era, dinosaurs were the dominant terrestrial vertebrates, ruling the Earth for over 160 million years.
Marine Reptiles: At different points in history, various marine reptiles, such as ichthyosaurs, plesiosaurs, and mosasaurs, were the dominant predators in Earth's oceans.
Insects: Insects have been and continue to be highly successful and dominant in terms of sheer numbers and ecological impact. They play crucial roles in pollination, decomposition, and as a food source for many other creatures.
Microorganisms: Throughout Earth's history, microorganisms like bacteria and archaea have been the most abundant and widespread forms of life.
Mammals: After the extinction of the dinosaurs around 65 million years ago, mammals underwent a period of adaptive radiation, leading to the rise of various mammalian groups. Today, mammals have become a dominant and diverse group of animals, including humans.
It's important to understand that the concept of "dominance" in the natural world is not necessarily about a species exerting control over others. Instead, it's about a species' ability to adapt to its environment, find resources, and successfully reproduce and pass on its genes to future generations. The notion of dominance is context-dependent and can vary based on the specific ecological niche and the dynamics of the ecosystem.
In the absence of human dominance, Earth would likely continue to support a rich diversity of life, with various species occupying different roles within ecosystems, contributing to the balance and functioning of the planet's biodiversity.