Ages (historic periods of time)

Known as "periodization", the categorization of periods of time according to general technological characteristics

Periodization

categories help to characterize periods of time for easy reference
however, these categories are helpful in the general and not the specific applications
- i.e., a period of time may fall into one category, but that does not mean that every population or civilization follows that particular characterization
ex.

Periods
	Paleolithic	Nelolithic	Bronze Age	Iron Age
<12,000 BC	✓+
12,000 BC	✓+	✓-
4,000 BC	✓	✓	✓-
1000 BC	✓-	✓+	✓	✓-
1 AD	✓-	✓-	✓-	✓+

the idea is that while farming may have developed in some places, hunting and gathering continued in most other places, until farming spread everywhere.
so each of these "Ages" or "Periods" existed coincidentally
additionally, social and political organization existed coincidentally within and across each of these periods
for an historic example of a person who lived in three periods at once see Otzi the Iceman

General dates per onset of subsequent age
Paleolithic	Neolithic	Copper Age	Bronze Age	Iron Age
rise of mankind to 12,000 BC	12,000 BC to 4,000 BC	5,000-3,000 BC	3,300-1,100 BC	1,000 BC to 550 BC
Stone Age		Chalcolithic period, use of copper but mostly stone tools
Prehistory (before writing)
stone tools and other hand-made or natural objects		copper smelting (heating, separating from other elements, and shaping into tools through molds)
some pottery, baskets	pottery, baskets, ovens, farm tools

See:

When putting together a chronological presentation of ancient artifacts, early 19th century archeologist C. J. Thomsen found that the objects stood out in the three groups of stone, bronze and iron.
the ancient writers Hesiod (Greek) and Lucretius (Roman) grouped human history into "progressive" periods, i.e. either degrading or advancing from one to the other:
- Hesiod's Ages of Man is a degradation: Golden, Silver, Bronze, Heroic and Iron.
- Lucretius' is a progression: "Everything must pass through successive phases. Nothing remains forever what it was. Everything is on the move. Everything is transformed by nature and forced into new paths..."
Periodization is mostly used for archaeological categorization
for students, it is helpful to understand social and political structures, population growth, and trade and other forms of cultural diffusion