They're both correct. "Thanks" is slightly more informal, but otherwise, they both mean the same, a statement of gratitude.
Although they're both correct, they have a difference.
"Thanks" is a noun, and can be used like this:
Give James my thanks./ I give you my thanks.(when speaking face to face)
Hence, the today's expression, "Thanks, Jim".
"Thank you", the "thank" is a verb, and is actually a shortening of the phrase "I thank you". So, you'd probably not say "Give Jim my thank-you", but "Give Jim my thanks."
Otherwise, they are interchangeable.
Traits of the kind that you mention can be classed as demographic characteristics or demographic features.
According to the definitions supplied by Oxforddictionaries.com, demography has two denotations:
1 The study of statistics such as births, deaths, income, or the incidence of disease, which illustrate the changing structure of human populations.
1.1 The composition of a particular human population.
Best Answer
"From an early age" sounds much more natural. The phrase should be followed immediately in the sentence by a noun or pronoun representing the person to whom the phrase applies.