Reading 25

Neanderthals

The following passage is adapted from an article entitled “The Mysterious Downfall of the Neanderthals” (2009 Kate Wong).

1. Ever since the discovery of the first
2. Neanderthal fossil in 1856,
3. scientists have debated the place
4. of these bygone humans on the
5. family tree and what became of
6. them. For decades two competing
7. theories have dominated the
8. discourse. One holds that
9. Neanderthals were an archaic
10. variant of our own species, Homo
11. sapiens, that evolved into or was
12. assimilated by the anatomically
13. modern European population.
14. The other posits that the
15. Neanderthals were a separate
16. species that modern humans
17. swiftly extirpated on entering the
18. archaic hominid’s territory.
19. Over the past decade, however,
20. two key findings have shifted the
21. fulcrum of the debate away from
22. the question of whether
23. Neanderthals and moderns made
24. love or war. One is that analyses
25. of Neanderthal DNA have yet to
26. yield the signs of interbreeding
27. with modern humans that many
28. researchers expected to see. The
29. other is that improvements in
30. dating methods show that rather
31. than disappearing immediately
32. after the moderns invaded Europe,
33. starting a little more than 40,000
34. years ago, the Neanderthals
35. survived for nearly 15,000 years
36. after moderns moved in.
37. These revelations have prompted
38. a number of researchers to look
39. more carefully at other factors that
40. might have led to Neanderthal
41. extinction. One of the most
42. informative new lines of evidence
43. bearing on why the Neanderthals
44. died out is paleoclimate data.
45. Scholars have known for some time
46. that Neanderthals experienced
47. both glacial conditions and milder
48. interglacial conditions. In recent
49. years, however, analysis of
50. primeval isotopes have enabled
51. investigators to reconstruct a far
52. finer-grained picture of the climate
53. shifts that occurred during a period
54. known as oxygen isotope stage 3
55. (OIS-3). Spanning the time
56. between roughly 65,000 and
57. 25,000 years ago, OIS-3 began
58. with moderate conditions and
59. culminated with the ice sheets
60. blanketing northern Europe.
61. Considering that Neanderthals
62. were the only hominids in Europe
63. at the beginning of OIS-3 and
64. moderns were the only ones there
65. by the end of it, experts have
66. wondered whether the plummeting
67. temperatures might have caused
68. the Neanderthals to perish. Yet
69. arguing for that scenario has
70. proved tricky for one essential
71. reason: Neanderthals had faced
72. glacial conditions before and
73. persevered.
74. In fact, numerous aspects of
75. Neanderthal biology and behavior
76. indicate that they were well suited
77. to the cold. Their barrel chests and
78. stocky limbs would have conserved
79. body heat, and their brawny build
80. seems to have been adapted to
81. their ambush-style hunting of
82. large, relatively solitary mammals
83. that roamed northern and central
84. Europe during the cold snaps.
85. But the isotope data reveal that far
86. from progressing steadily from
87. mild to frigid, the climate became
88. increasingly unstable heading into
89. the last glacial maximum. With that
90. flux came profound ecological
91. change. So rapid were these
92. oscillations that over the course
93. of an individual’s lifetime, all the
94. plants and animals that a person
95. had grown up with could vanish
96. and be replaced with unfamiliar
97. flora and fauna. And then, just as
98. quickly, the environment could
99. change back again.
100. It is this seesawing of
101. environmental conditions that
102. gradually pushed Neanderthal
103. populations to the point of no
104. return, according to scenarios
105. posited by such experts as
106. evolutionary ecologist Clive
107. Finlayson. These shifts would have
108. demanded that Neanderthals adopt
109. a new way of life in very short
110. order. For example, the
111. replacement of wooded areas with
112. open grassland would have left
113. ambush hunters without any trees
114. to hide behind. To survive, the
115. Neanderthals would have had
116. to alter the way they hunted.
117. Some Neanderthals did adapt to
118. their changing world, as evidenced
119. by shifts in their tool types and
120. prey. But many probably died out
121. during these fluctuations, leaving
122. behind ever more fragmented
123. populations. Under normal
124. circumstances, these archaic
125. humans might have been able to
126. bounce back, as they had previously.
127. This time, however, the rapidity
128. of the environmental change left
129. insufficient time for recovery.
130. Eventually, the repeated climatic
131. insults left the Neanderthal
132. populations so diminished that
133. they could no longer sustain
134. themselves.