1. The history of Maize domestication

2. A Brief Prehistory of Mexico
Time before the
present b.p.
Mirambell
(2000)
Zeitlin y Zeitlin
(2000)
4,000 - Neolítico Formative
5,000 - 4,000 Protoneolítico Late Archaic
7,000 - 5,000 Protoneolítico Middle Archaic
12,000 - 7,000 Cenolítico
superior
Early Archaic
35,000-12,000 Cenolítico inferior Late Paleo-Indian
? to 35,000 Arqueolítico Early Paleo-Indian
2,000

3. Early microfossil
evidence for
maize in
archaeological
contexts.

4. Sites of the Protoneolithic period

5. Archaeological
context of the
Protoneolithic
Period
(1)

6. Archaeological
context of the
Protoneolithic
Period
(2)
Figures from Ranere et al, 2009

7. Morphological Characters
studied on archaeological maize
1. Specimen Condition
2. Specimen Length
3. Cob Diameter
4. Rachis Diameter*
5. Pith Diameter*
6. Row Number*
7. Cupule Width*
8. Cupule Depth
9. Rachid Length*
* Show significant variation over
time

8. San MarcosCoxcatlanEl Riego

10. Calculating evolutionary rates
• Calculation of rates of change follows Haldane
(1949):
Darwin = ln(x2) - ln(x1) / t
Where ln is the logarithm base e, x1 and x2 are
the later and earlier average specimen
dimension and t is the length of time
separating the two specimens.

11. San MarcosCoxcatlanEl Riego

12. Evolutionary rates in Wheat
(after Tano and Willcox 2006)
Postulated allele frequencies of indehiscent (d) and dehiscent (D) over 10000 +
radiocarbon years of Middle Eastern prehistory (left) and relative fitness of geno-
types of wild wheat. While selection for indehiscent phenotypes appears to have
Occurred gradually, selection is not continuously increasing. This is similar to
the puntuated pace of evolutionary change in maize in Mesoamerica

13. Conclusions
• The antiquity of human manipulation of maize is suggested
by maize and teosinte microfossils in some areas of the
Americas, this evidence does not yet indicate the impact of
human selection on maize.
• Contemporaneous Protoneolithic sites in Mesoamerica are
discordant about time and place of domestication.
• Study of inflorescence morphology shows the intensity of
human selection on maize is greatest around the 5th
millenium BP cal.
• Human selection intensity on maize is not continuous, in a
similar way to that of the Middle East where local effects –
environmental variation between and within sites over time
– affect the cultivator’s ability to monitor and act on the
effects of selection.