the coastal refuge hypothesis

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Jul 31, 2022, 10:20:19 AMJul 31
Relevance of the eastern African coastal forest for early hominin biogeography
Josephine CA Joordens cs 2019 JHE 131:176-202
doi org/10.1016/j.jhevol.2019.03.012 open access

The influence of climate change on hominin evolution is much debated.
2 issues hamper our understanding of this process:
- the limited hominin fossil record,
- incomplete knowledge about hominin spatial occupation of Africa.

Here, we analyze the presently known hominin fossil distribution pattern,
we explore the potential geographic distribution of hominins between ∼4.5 & ∼2.5 Ma.
We focus on assessing the relevance of the Coastal Forest of E-Africa (CFEA) along the Indian Ocean as a core area for early hominin evolution.
Based on bio-geographic-phylo-geographic data, we propose the coastal refuge hypothesis:
the CFEA provided a refugium for early hominins in periods of variable climate & strong seasonality during eccentricity maxima.
From this refuge, evolved spp could disperse inland (e.g. to rift basins) via vegetated humid corridors, whenever onset of stable climate periods with low seasonality during eccentricity minima allowed expansion out of the coastal enclave.
We develop a conceptual model in time & space, comparing predictions with climatic & hominin fossil records.
The results imply
1) between ∼4.5 & 3 Ma, ongoing (mostly anagenetic) hominin evolution occurred in the CFEA, punctuated by inland dispersal events at ∼4.4, 4.2, 3.8, 3.5 & 3.2 Ma;
2) before ∼3 Ma, the Afar Basin was a (sub)core area often connected to & rel.similar to the CFEA, while other inland areas were more or less marginal for early hominin habitation;
3) after ∼3 Ma, N-Hemisphere Glaciation exerted strong influence by causing latitudinal contraction of the CFEA, leading to habitat fragmentation, isolation of hominin populations & possible cladogenetic evolution.

A major challenge for the coastal refuge model is:
at present, no (hominin) fossils are known from the CFEA.
We consider how this can be explained, and possibly overcome with targeted search efforts.
Furthermore we discuss how the model can be
- tested, e.g. with molecular phylo-geography approaches,
- used to predict new hominin fossil locations.
With this study, we hope to contribute a fresh perspective to the climate-evolution debate, emphasizing the role of climatic stability, length of dry season & vegetation cover, to facilitate connectivity between hominin core & marginal habitats.


Jul 31, 2022, 4:48:59 PMJul 31
For the record:

I believe that the Quaternary Period, the glacial/interglacial cycle was the major
driver of this through the lifespan of Homo. But, it probably was going to happen
anyway only it would have taken orders of magnitude longer.

Plate tectonics didn't create "The Ice Age." It more or less predisposed us to
glaciations. It changed the currents. Most of the sun's energy falls along the
equator, the currents redistribute that energy across the globe. Change the
currents and you change that distribution. Cold spots form. And it took
HUNDREDS OF THOUSANDS of years but eventually the cold seeped down
even to deep ocean waters, and from there the glacial periods started to grow

The oceans are a battery, storing and releasing energy from the sun. They're
not warming, the deep waters are what's important here, the surface
temperatures fluctuate easily, which is why the fake science that is AGW
invented some non existing concept called "Ocean Memory" and started
babbling about how the ocean lost it's memory...

What they mean is that the data conclusively demonstrates no warming what
so ever. Well that contradicts the narrative, so now they pretend that the
ocean "Forgot" that it warmed... that's why it's not warmer... it simply "Forgot."

Anyway, all this really hit it's stride about a million years ago, so that's where
I'd look for everything being turbo charged...

But I honestly think you're right, that modern man basically began with your
erectus, and certainly before 1 million years ago, but "Climate Change"
would have been at it's biggest, as a factor, starting then.

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