Reply to Comment on Franz et al. (2023): A reinterpretation of the 1.5 billion year old Volyn ‘biota’ of Ukraine, and discussion of the evolution of the eukaryotes, by Head et al. (2023)
Abstract. Head et al. (2023) emphasize the importance of the Volyn biota for the evolution, especially in the so-called ‘boring billion’, in a detailed outline about the biological and geological context. However, they question that the Volyn biota represent Precambrian fossils and instead argue that they are young contaminants of ‘museum dust’. In addition, they postulate that they are of abiotic origin. We present here a detailed discussion of their points of concern based on presented data, including some additional information. Their points of concern were:
- One object, shown by Franz et al. (2023) is similar to a pollen grain, another object is similar to trichomes; we show indications for fossilization and summarize our arguments against ‘museum dust’.
- They question the fossil character of the biota and argue for a biomineralization; we show that the biomineralization in trichomes is distinct from the mineralization of the biota.
- They missed information about the internal structure; we repeat the presented information about the internal structure in more detail, which is also indicative of fossil material and inconsistent with trichomes.
- They argue that we did not compare via infrared spectroscopy the biota with recent fungi; since the biota experienced temperatures near 300 °C, we think that a comparison with thermally degraded chitosan is more appropriate.
- They question the use of strongly negative δ13C as an argument for biotic origin, but we show that in combination with positive δ15N values and the geological situation, a biotic origin is more likely than abiotic synthesis.
In addition, Popov (2023) questioned the age of the Volyn biota, which we postulated as between approximately 1.5 and 1.7 Ga. He argues that the fossils could be Phanerozoic. We will also outline our arguments for the minimum age of 1.5 Ga.
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