I feel like this part of evolution is kind of skipped over by historians. The more I think about it the more it hurts my brain
In: Biology
We don’t *really* know.
There are many theories and proposals of key processes that most likely played a significant role, but we can’t be exactly sure.
One of the big processes proposed is colonization and specialization.
Single-cell organisms most likely started to form colonies and clusters that improved their ability to protect against predators, easier to find resources, and more efficient reproduction. This allowed cells to specialize into specific tasks, such as some cells specifically for defense, some for reproduction etc. At this point, you can basically call it a multi-cell organism, since an incredibly simple description of the colloquial term “organism” is a colony of cells that are connected and working together to keep the organism alive and reproduce. However, much more technically, this is not close to detailed enough as we’re still missing out on the changes in genetic regulation of behavior, how they could communicate specific division of labor and specialization, designate when specific cells with specific specializations should divide, how they communicated to differentiate each other etc., not to mention genetic mechanisms for cell adhesion and apoptosis (programmed, intentional, cell death), which are absolutely critical factors for a multi-celled organism to survive.
There is also a high likelihood that different forms of life had different processes that lead to their current form. Animals most likely evolved from some form of single-celled protozoa and plants most likely evolved from single-celled green algae.
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