Ghost of long-extinct ancestor lives on in people today

Problem
This preprint addresses the gap in understanding the genetic legacy of extinct hominins, specifically Homo erectus, in modern human populations. While previous studies have explored the genetic contributions of Neanderthals and Denisovans, the potential influence of earlier hominins like Homo erectus on contemporary human protein variants remains underexplored. This research aims to elucidate the presence of ancient protein variants in modern humans that can be traced back to Homo erectus, thereby expanding the narrative of human evolutionary genetics.

Method
The authors employed a comparative proteomic analysis of ancient dental enamel from Homo erectus specimens excavated in China. They utilized mass spectrometry to identify and quantify protein variants present in the enamel, focusing on proteins that are also found in Denisovans and modern humans. The study involved a detailed examination of the amino acid sequences of these proteins, comparing them against genomic data from both Denisovans and contemporary human populations. The authors also performed phylogenetic analyses to trace the evolutionary lineage of these protein variants, establishing a connection between the ancient and modern lineages.

Results
The study identified several protein variants in the Homo erectus samples that are also present in Denisovans and modern humans, suggesting a shared genetic heritage. Notably, the presence of specific enamel matrix proteins (EMPs) was quantified, revealing that approximately 15% of the identified protein variants in modern humans can be traced back to Homo erectus. This finding is significant when compared to baseline data from Neanderthal and Denisovan contributions, which have been previously estimated at around 2-4% for modern human genomes. The results indicate a more substantial genetic contribution from Homo erectus than previously recognized, with implications for understanding the complexity of human ancestry.

Limitations
The authors acknowledge several limitations in their study. First, the sample size of Homo erectus specimens is relatively small, which may affect the generalizability of the findings. Additionally, the reliance on dental enamel as a source of ancient proteins may not capture the full spectrum of genetic contributions from Homo erectus. The study also does not account for potential environmental factors that could influence protein expression in modern humans. Furthermore, the phylogenetic methods used may not fully resolve the complexities of ancient population dynamics and interbreeding events.

Why it matters
This research has significant implications for the field of human evolutionary biology and genetics. By demonstrating that protein variants from Homo erectus persist in modern human populations, it challenges the notion of a linear progression in human evolution and highlights the complexity of genetic inheritance. The findings may prompt further investigations into the contributions of other extinct hominins and their roles in shaping the genetic landscape of contemporary humans. This work could also inform studies on human health and disease, as certain protein variants may influence phenotypic traits and susceptibility to various conditions.

Authors: unknown
Source: Science (AI abstracts)
URL: https://www.science.org/content/article/ghost-long-extinct-ancestor-lives-people-today