Another Problem For Milankovitch: Megaflora of the Ice Age?

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Discussion Overview

The discussion centers on the relationship between Milankovitch cycles and the existence of megaflora and megafauna during the Ice Age, particularly focusing on the size of primates and trees in the Amazon rainforest. Participants explore the implications of climatic changes on biological forms and the potential discrepancies in established theories regarding glacial conditions and vegetation growth.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants suggest that the size of Pleistocene tree-top monkeys, such as Caipora bambuiorum, indicates that Amazonian trees were significantly larger during the Ice Age, potentially due to increased biomass rather than solely climatic factors.
  • Others question the connection between Milankovitch cycles and biological mega forms, arguing that temperature and aridity changes may have had a more substantial impact on species survival and size.
  • A participant proposes that the increase in rainforest biomass contradicts the expectations of Milankovitch theory, which suggests reduced insolation and colder conditions during glacial periods.
  • Another participant emphasizes that Milankovitch effects are more pronounced in polar regions, suggesting that the equatorial climate may not have followed the same patterns, and references studies indicating that Amazonian forests were not replaced by savanna during glacial periods.

Areas of Agreement / Disagreement

Participants express differing views on the implications of Milankovitch cycles for biological forms during the Ice Age. There is no consensus on the relationship between climatic changes and the size of flora and fauna, with multiple competing perspectives remaining unresolved.

Contextual Notes

Limitations include the need for appropriate references to support claims made by participants, as well as the complexity of the interactions between climate, vegetation, and animal size during the Ice Age, which remain under debate.

aspergers@40
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Not only grassland animals grew in size to mega proportions, but there's also evidence to suggest that some jungle animals did as well. The grasslands can perhaps be explained by increased aridity, but that alone can't explain twice size pleistocene tree-top monkeys, can it?

http://209.209.34.25/webdocs/anatomy/Brazil.htm

The skull of Caipora bambuiorum, one of the two complete primate skeletons recovered from Toca da Boa Vista. It closely resembles the living spider monkey, but is more than twice the size, suggesting that South American monkeys participated fully in the mega-faunal phenomenon of the last Ice Age.

Frontal view of the crania of Protopithecus (left) and Caipora (right), both from Toca da Boa Vista. They resemble living South American monkeys that inhabit the top levels of the tropical forest canopy, but they were significantly larger than any living species. Further exploration of Toca da Boa Vista hopefully will yield more primate species that also were quite large compared to modern monkeys.

The trees must have grown much larger, surely? More sunshine from reduced cloud cover can't explain all of the growth, could it?
 

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I don't get the connection between Milankovitch and biologic mega forms.

Is there doubt about advancing glacial features during the Pleistocene? Not that I know of. Also there are several conflicting temperature signs and indeed changing aridity regimes may have had even a bigger impact.

Maybe many megaforms died out because they were too specialized, but that may not be related predominantly to temperature rather than aridity. One could argue that the European straight tusked Elephant did not die out because of dropping temperature but rather due to disappearing forests in the arid late Pleistocene (Weichelian) as the youngest remains in the NL was dated 32500 years ago, long after the last interglacial (Eemian/Sangamonian), 130-115 thousand years ago
 
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Thanks for the reply. I think that the monkey skulll finds indicate that the amazonian trees where they lived were twice as big, with twice as big fruit, hence bigger monkeys! The decrease in precipitation could be responsible for some of it, but the evidence suggests a blooming increase in the biomass of the rainforest which isn't normally associated with glacial conditions. Milankovitch theory describes a reduced insolation due to it's 100,000 year eccentricity cycle i.e. it gets colder because we move further away from the sun. A near-doubling of rainforest tree-tops isn't indicative of a weaker sun, is it? Could the ice age cooling be due to something else other than Milankovitch solar forcing?
 
Hold it, that's all very tentative. Firstly the effects of the Milankovitch cycles are largest in the polar areas, especially obliquity, while at the equator the effects are much less, mostly we have to think in sine's about the angle of the sun. So at the equator we talk in sine (90 +/- 22 degrees) for energy and solar angles but at in artics that would be order of magnitudes of sine (20 +/- 22 degrees).

There are a few studies that point to erratic temperature indications for the Amazon, for instance http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WPN-45FJXN9-17&_user=10&_coverDate=01%2F31%2F1999&_alid=1150400126&_rdoc=1&_fmt=high&_orig=search&_cdi=6995&_sort=r&_docanchor=&view=c&_ct=7&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1c468f1d81080e088ae386c97ce49715:

This comparison shows that the Amazon Basin forests were not extensively replaced by savanna vegetation during the glacial period, contradicting the refugia hypothesis.

So it has been noted before and indeed there are plenty more studies like this one challenging ice age paradigms, which form the basis of AGW.
 
Locked pending moderation.

Update:
The OP has not provided appropriate references to back up statements, thus the thread will remain closed.
 
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