A New Hypothesis for the Origin of Multicellular Life: A Microbial Fusion Perspective

The origin of multicellular life is one of the most fundamental questions in evolutionary biology. The prevailing view holds that multicellular organisms arose from clonal cell groups of a single-celled eukaryote that failed to separate after division, followed by cell differentiation for functional division of labor. This paper proposes an alternative hypothesis: multicellular organisms initially arose through the aggregation, division of labor, and genetic fusion of multiple distinct microbial species. In this hypothesis, different microbes gathered under environmental pressure; driven by functional specialization, they each lost redundant genes; and ultimately, through horizontal gene transfer and chromosomal integration, they fused into a unified organism sharing a common genome. This paper also discusses how the probability of gene fusion decreases with increasing biological complexity while environmental stress can transiently elevate this probability, and analyzes the compatibility of this hypothesis with existing biological evidence.