Rise of collagen-eating microbes may help explain gaps in the fossil record

The fossil record has long presented paleontologists with fascinating contradictions. While hard-shelled organisms and heavily mineralized bones readily fossilize under the right geological conditions, soft-bodied creatures almost always decompose before they can leave a permanent impression in the rock strata. However, exceptional fossil deposits, known as Lagerstätten, have occasionally preserved fragile, soft-bodied organisms from the Ediacaran and early Cambrian periods, presenting scientists with delicate impressions of creatures that were essentially fragile bags of goo.

For decades, the mechanisms behind the preservation of these delicate organisms remained poorly understood. Researchers generally assumed that rapid burial in anoxic environments was the primary driver of soft-tissue preservation. Yet, this traditional view failed to account for why older, delicate organisms were frequently preserved while many younger, evolutionarily advanced soft-bodied animals left virtually no trace in subsequent geological eras. A missing variable in the equation pointed directly to the microscopic world and the evolution of biological decay agents.

Recent investigations into microbial ecology suggest that the rise of specific collagen-eating bacteria and microorganisms dramatically altered the dynamics of fossilization over geological time scales. Collagen is a primary structural protein found in the extracellular matrix of animal tissues. In the earliest stages of animal evolution, before specialized decomposer microbes evolved to efficiently target and digest collagen, dead organisms stood a higher chance of mineral replacement before their structural integrity completely collapsed.

As ecosystems evolved and biological diversity expanded, microbial communities also adapted. The emergence of efficient collagen-degrading microbes meant that dead organic matter was broken down much more rapidly and thoroughly than in earlier epochs. This biochemical shift effectively raised the bar for soft-tissue preservation, leaving only the most uniquely fortuitous burial events capable of rescuing soft-bodied specimens from total microbial consumption.

This insight helps explain significant gaps in the fossil record by reframing fossilization not merely as a passive geological accident, but as an active biological competition between preservation processes and microbial decay. When ancient ecosystems lacked specialized collagen-eating organisms, soft tissues persisted longer in sediment, allowing mineralizing waters sufficient time to cast their shapes into stone.

Ultimately, this research bridges a crucial gap between microbiology and paleontology. By acknowledging the profound impact that microscopic decomposers had on ancient remains, scientists can refine their interpretations of evolutionary history. The invisible work of ancient microbes thus holds the key to reading the visible history of life on Earth.