https://www.sciencedaily.com/releases/2019/10/191007153451.htm
October 7,2019

To understand the environmental pressures that shaped human evolution,
scientists
must first piece together the details of the ancient plant and animal
communities that
our fossil ancestors lived in over the past 7 million years. Because
putting together the
puzzle of millions-of-years-old ecosystems is a difficult task, many
studies have
reconstructed the environments by drawing analogies with present-day African
ecosystems, such as the Serengeti. A study led by a University of Utah
scientist calls
into question such approaches and suggests that the vast majority of human
evolution
occurred in ecosystems unlike any found today. The paper was published
online today
in the Proceedings of the National Academy of Sciences of the United
States of
America.

To test for differences between modern and ancient environments, the
researchers
analyzed a dataset of more than 200 present-day African mammal communities
and
more than 100 fossil communities spanning the past 7 million years in
eastern Africa,
a time period encompassing all of human evolution. They found that prior
to 700,000
years ago, mammal communities looked far different from those today. For
example,
fossil communities supported a greater diversity of megaherbivores,
species over
2,000 pounds, such as elephants. Likewise, the dietary structure of fossil
communities
frequently departed from those seen today, with patterns of grass- and
leaf-eating
species fluctuating in abundance. Around 1 million years ago, fossil
communities began
transitioning to a more modern makeup, which the authors suggest is the
likely the
outcome of long-term grassland expansion coupled with arid climate pulses.
The new
paper adds to growing evidence that scientists need to critically
re-evaluate our
understanding of the ancient ecosystems in which early humans evolved.

"For a long time, our field has been trying to pin down how environmental
changes
influenced human evolution, but we've got to be able to reconstruct past
environments
right in the first place," said lead author Tyler Faith, curator of
archaeology at the Natural
History Museum of Utah and assistant professor of anthropology at the U.
"If we continue
to reconstruct ancient environments on the basis of modern African
ecosystems, we are
likely missing an entire realm of possibilities in how past ecosystems
functioned. Our
study invites our fellow researchers to think more critically about that."
....
For example, modern African ecosystems are dominated by ruminants --
relatives of
cows and antelopes that have four compartments in their stomachs to
thoroughly break
down food. Non-ruminants equipped with simple stomachs are comparatively
rare, with
at most eight species coexisting in the same area today. Non-ruminants,
including
relatives of elephants, zebras, hippos, rhinos and pigs, are like
digestive conveyor belts,
said Faith. They eat larger quantities of plants to make up for their
inefficient digestion.
In contrast to the present-day pattern, eastern African fossil records
document landscapes
rich in non-ruminant communities, with dozens of species co-existing
within the same area.
....

The paper is open access.

https://www.pnas.org/content/116/43/21478
Early hominins evolved within non-analog ecosystems

Significance
Testing ecological hypotheses of human evolution requires an understanding
of the
ancient plant and animal communities within which our ancestors lived. Though
present-day ecosystems provide the baseline for reconstructing the
ecological context
of human evolution, the extent to which modern ecosystems are
representative of past
ones is unknown. Through analyses of a fossil dataset spanning the last 7
Myr, we show
that eastern African communities of large-bodied mammalian herbivores
differed
markedly from those today until ∼700,000 y ago. Because large herbivores are
ecosystem engineers and shape biotic communities in ways that impact a
wide variety
of species, this implies that the vast majority of early human evolution
transpired in
the context of ecosystems that functioned unlike any known today.

Abstract
Present-day African ecosystems serve as referential models for
conceptualizing the
environmental context of early hominin evolution, but the degree to which
modern
ecosystems are representative of those in the past is unclear. A growing
body of
evidence from eastern Africa’s rich and well-dated late Cenozoic fossil
record
documents communities of large-bodied mammalian herbivores with ecological
structures differing dramatically from those of the present day, implying
that modern
communities may not be suitable analogs for the ancient ecosystems of hominin
evolution. To determine when and why the ecological structure of eastern
Africa’s
herbivore faunas came to resemble those of the present, here we analyze
functional
trait changes in a comprehensive dataset of 305 modern and fossil herbivore
communities spanning the last ∼7 Myr. We show that nearly all communities
prior
to ∼700 ka were functionally non-analog, largely due to a greater richness of
non-ruminants and megaherbivores (species >1,000 kg). The emergence of
functionally modern communities precedes that of taxonomically modern
communities
by 100,000s of years, and can be attributed to the combined influence of
Plio-Pleistocene C4 grassland expansion and pulses of aridity after ∼1 Ma.
Given the
disproportionate ecological impacts of large-bodied herbivores on factors
such as
vegetation structure, hydrology, and fire regimes, it follows that the
vast majority of
early hominin evolution transpired in the context of ecosystems that
functioned unlike
any today. Identifying how past ecosystems differed compositionally and
functionally
from those today is key to conceptualizing ancient African environments
and testing
ecological hypotheses of hominin evolution.

Lol!

In order to study the environments of our ancestors you must first look for
our ancestors and their environments, instead of digging out fossils only
where it's convenient and then pretending that anything you find must be
an ancestor.

"The Biggie," of course, is the Quaternary Period, the present ice age, and
the Glacial/Interglacial cycle. Sea level rose & fell, the planet grew wetter
and drier, weather patterns were radically transformed as were ecosystems...

https://prd-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/atom_page_medium/public/thumbnails/image/wss-cycle-oceans-map-past-coastline.gif

Humans never lived very far from the water, so when the coast was THAT
far out, and it was, where should you be looking for humans?

Hmm?

And I know that image is of North America but it was the same story
virtually everywhere. And it's the coastline that was the highway our
ancestors took to migrate from one continent to another...

So if you want to know how the environment impacted our ancestors,
you need to start by rejecting the laughing stock which is paleo
anthropology and you've got to start looking for our ancestors in their
environment... under what is now the sea.

-- --

https://jtem.tumblr.com/post/655544372737327105