A fossil is any preserved remains, impressions, or traces of any once-living organism(s) imprinted in rocks that enable its identification as being from a (past) geological age.
Since organisms started to inhabit the Earth’s surface, body decomposition is the norm after their death, affecting the great majority of organisms. For fossilization to happen, it means that decomposition cannot happen, which is, at Earth’s surface, extremely rare.
Still, some body parts of organisms that are calcium-rich (like teeth, shells, bones, and so forth) can stand for thousands (sometimes millions) of years without being decomposed, also becoming fossils.
Despite a combination of a recently developed better understanding of plate tectonics theory and technological advances in radiometric dating (the rates at which various radioactive elements decay show how long ago they were incorporated into the rock), it is still challenging for paleontology to work out fossil ages (especially isolated bones and teeth) because the beds that preserve the fossils are typically lacking the radioactive elements (common only in rocks with a volcanic origin) necessary for accurate dating.
On the other hand, the fossilization of a whole organism (which requires that decomposition does not happen) is often associated with ultra-rare events triggered by toxic (and anoxic) gas eruptions from the mantle (usually happening in deep lakes) spanning from 1.000.000.000 to 37 years ago. Those anoxic events generate fossil sites with exceptional preservation (called lägerstatten – German for storage places) that are fairly distributed throughout the Earth’s surface.
Because of all those difficulties in fossilization itself, today, it is generally accepted by paleontology that the fossil record is vastly incomplete (only less than 5% of the number of known living species have been discovered through fossils, suggesting that the number of species known through fossils must be far less than 1% of all species that ever lived) and that its interpretation is filled (and fuelled) with cultural biases.
Those technological difficulties in dating fossil findings, together with the rarity of its appearance, are compounded by the way paleontologists often call a single sample like a bone or tooth a new “species,” which in this case means more something like a “specimen” and therefore should not be taken as the definition of species as we see in biology
The largest group of organisms whose males and females can mate and reproduce, generating fertile offspring.
It is important to highlight that a fossil find is nothing more than the remains of a single organism.
A single organism can represent a species (biology) to the extent that this representation is not used to infer over whole populations (within organisms belonging to the same species, it is common to find different diets, social behaviors, morphology, and so forth).
Specifically, in the case of primates (humans included), the fossil record is mainly composed of scattered remains like teeth and bone fragments, with lägerstatten with primates being extremely rare (to illustrate, this is a world map of primate fossil finds (humans included), with the ages of the fossils and the places they were found).
The nature of the primate fossil record poses a challenge for accurate dating, while making the analysis of the specimens’ age, gender, and morphology difficult. Also, due to the lack of technological development, even primate fossil findings that were done many years ago could have their analyses done just recently.
When contextualizing the findings of primate fossil records, instead of using contemporary notions of geography without taking into consideration the actual environmental conditions found at Earth’s surface (something fundamental, such as the position of the continents, for example), attaching human fossil finds to contemporary cultures as a totem could become a huge historical and scientific mistake.
Within the primates, at least all humans inhabiting Earth’s surface today are part of the same species (biologically speaking); therefore, a fossil specimen, no matter how old or significant, should not be conflated with a biological species, nor should it be used to anchor cultural identity.
The fossil record is a small sample humans have throughout the time of a vast, chaotic, complex, and still waiting-to-be-understood system found in the biosphere.
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