Trees usually add growth rings on a yearly basis, with the spacing of rings being wider in high growth years and narrower in low growth years.
Patterns in tree-ring growth can be used to establish the age of old wood samples, and also give some hints to local climatic conditions.
DNA analysis is an examination method that emerged in the 1980s and is credited to Alec Jeffreys, an English geneticist. Analysis of DNA allows any type of organism to be identified by analyzing its genetic sequences.
This method can also clarify questions of identification within a species.
DNA analysis is usually performed by forensic scientists.
In instances where individuals need to be identified, the forensic scientists tend to employ a method of scanning 13 regions of the human genome.
Identification within a species can present more of a challenge than determining between two different species.