This document provides a brief history of dendrochronology, or tree-ring dating. It traces the field back to early observations by Leonardo da Vinci and Theophrastus on tree growth patterns. Several 18th century scientists like Duhamel du Monceau and Buffon made further contributions. Andrew Ellicott Douglass, considered the founder of the modern field of dendrochronology, developed the technique of cross-dating tree rings in the early 20th century. This allowed the calibration of floating tree-ring chronologies to calendar years and the dating of archaeological sites and ruins in the American Southwest.

1. October 25
The history of dendrochronology

2. “ RINGS
”
IN THE BRANCHES OF
SAWED TREES SHOW
THE NUMBER OF YEARS
AND, ACCORDING TO THEIR
THICKNESS,
THE YEARS WHICH WERE
MORE OR LESS
DRY.
Leonardo da Vinci

3. “ ... and if one forces a stone or similar object into a
tree, it becomes hidden, since the new growth
surrounds it, as was the case with the wild olive tree
”
which stood in the market place at Megara.
Theophrastus
(371 - 287 BC)
Photograph: Anshul Nigham

4. Henri-Louis Duhamel du Monceau Georges-Louis Leclerc, Comte de Buffon
1700 - 1782 1707 - 1788

5. Frost ring Pinus sibirica
Photograph: Fri s Schweingruber

6. 1737
➟1708

7. Alexander Twining
1801 - 1884

8. “...every tree told the same story.”

9. Tucson, AZ

12. ANDREW ELLICOTT
DOUGLASS

13. Flagstaff, AZ

14. Andrew Douglass (right) Flagstaff 1898

15. Lowell Observatory Flagstaff Arizona
Source: Sam Wise

17. Source: Schiaparelli (1888)

18. Tucson, AZ

22. Photograph: Howard Arno

23. Photograph: Christine and John Fournier

24. “ We do not know how old these ruins are, but I should be
glad to have an opinion from you as to whether it might
be possible to connect up with your modern and dated
trees specimens [with wood specimens] from these
”
[prehistoric] ruins by correlating the curves of growth…
Clark Wissler to A.E. Douglass
1909

25. Aztec Ruin
Publo Bonita

26. Aztec Ruin National Monument New Mexico
Source: Sco Catron

27. Pueblo Bonito New Mexico
Source: Chris M

28. Pueblo Bonito New Mexico (before it was excavated)

29. Source: Stones 55

30. Wupatki New Mexico

31. Living-tree chronology
1300 1400 1500 1600 1700 1800 1900
‘Floating’ chronology

32. National Geographic ‘Beam Expeditions’ 1923 and 1929

34. Show Low, AZ

35. $5
for
100 rings

36. $65 2011 dollars
for
100 rings

38. Living-tree chronology
1300 1400 1500 1600 1700 1800 1900
1237 1380 HH-39
700 800 900 1000 1100 1200
‘Floating’ chronology

39. “ For the three of us, the experience was unforge able. To be
present at the instance of the celebrated breakthrough in
science that set the chronological house in order for the
Southwestern United States was reward enough. But beyond
”
that, was the privilege to work for a time at the side of
Douglass, the scholar, the astronomer turned archaeologist.
Emil Haury
1962

41. Tree-ring display at elementary school
Photograph:Tom Swetnam

51. GEOG8280
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