Did the presumed first step in the transition of primitive cells include the loss of the cell wall?

The idea behind the transition of primitive cells—specifically prokaryotic cells—to more complex eukaryotic cells typically involves significant cellular changes, including interactions with the environment. The loss of a rigid cell wall is indeed a plausible scenario that has been proposed as a contributing factor in the evolution toward more complex cellular structures. Cells with a flexible plasma membrane could develop endoplasmic reticulum and other membrane-bound organelles, which are characteristic of eukaryotic cells.

This transition would allow for greater cellular flexibility and complexity, potentially paving the way for the formation of organelles and a more sophisticated internal structure. Thus, assuming the loss of the rigid cell wall was one of the initial steps in this evolutionary process aligns with current hypotheses in evolutionary biology.

In contrast, the ideas of gaining a nucleus or remaining under investigation represent different aspects of the evolutionary story of cells. While the gaining of a nucleus is a significant development in eukaryotic evolution, it doesn’t necessarily relate directly to the initial loss of a cell wall. The idea that the entire evolution of cellular complexity is still under investigation reflects the ongoing research in this field but doesn't address the clarity around the loss of the cell wall as a primary step.