||Human Homo sapiens
||Lynnerup N, Kjeldsen H, Heegaard S, Jacobsen C, Heinemeier J. Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life. PLoS One. 2008 Jan 30 3(1):e1529. doi: 10.1371/journal.pone.0001529. p.3 left column 3rd paragraphPubMed ID18231610
||"[Researchers] have exploited the radical variations of the atmospheric 14C
content during the last 50 years to date the formation of the lens
crystallines. The concentration of 14C in living tissues reflects the
atmospheric 14C content at the time of growth. This is because
cosmogenic 14C in the atmosphere reacts with oxygen to form carbon dioxide (CO2), which is incorporated by plants, and then
ingested by animals...The nucleus of the human eye
lens contains 10–15 mg tissue, corresponding to approximately 3–
5 mg carbon, which is sufficient to perform a high precision
accelerator mass spectrometry (AMS)."
||"[Researchers'] results allow [them] to conclude that the crystalline formation in
the lens nucleus almost entirely takes place around the time of
birth, with a very small, and decreasing, continuous formation
throughout life. Such a life-long permanence of human tissue has
hitherto only been described for dental enamel [refs 1, 11]."