Humans are unique but not exceptional species of mammal

Date:
May 23, 2023
Source:
University of California - Davis
Summary:
Humans appear to resemble mammals that live in monogamous
partnerships and to some extent, those classified as cooperative
breeders, where breeding individuals have to rely on the help of
others to raise their offspring.


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FULL STORY ==========================================================================
In modern society, one parent may take a daughter to ballet class and fix dinner so the other parent can get to exercise class before picking up
the son from soccer practice. To an observer, they seem to be cooperating
in their very busy, co-parenting, monogamous relationship.

These people may think they are part of an evolved society different from
the other mammals that inhabit earth. But their day-to-day behavior and
child- rearing habits are not much different than other mammals who hunt, forage for food, and rear and teach their children, researchers suggest.

"For a long time it has been argued that humans are an exceptional,
egalitarian species compared to other mammals," said Monique Borgerhoff
Mulder, professor emerita of anthropology at the University of California, Davis, and corresponding author of a new study. But, she said, this exceptionalism may have been exaggerated.

"Humans appear to resemble mammals that live in monogamous partnerships
and to some extent, those classified as cooperative breeders, where
breeding individuals have to rely on the help of others to raise their offspring," she said.

The UC Davis-led study, with more than 100 researchers collaborating
from several institutions throughout the world, is the first to look
at whether human males are more egalitarian than are males among other
mammals, focusing on the numbers of offspring they produce.

The article, "Reproductive inequality in humans and other mammals,"
was published this week (May 22) in the Proceedings of the National
Academy of Sciences. Co-authors include researchers from UC Davis,
The Santa Fe Institute, the National Institute for Mathematical and
Biological Synthesis, and the Max Planck Institute for Evolutionary Anthropology, Germany.

The researchers amassed data from 90 human populations comprising
80,223 individuals from many parts of the world -- both historical and contemporary.

They compared the records for men and women to lifetime data for 45
different nonhuman, free-ranging mammals.

The researchers found that humans are by no means exceptional, merely
another unique species of mammal. Furthermore, as first author Cody Ross, former UC Davis graduate student in the Department of Anthropology now
at the Max Planck Institute, points out "we can quite successfully
model reproductive inequality in humans and nonhumans using the
same predictors." Egalitarianism in polygynous societies Somewhat unexpectedly, when focusing specifically on women, the researchers
found greater reproductive egalitarianism in societies that allow for polygynous marriage than in those where monogamous marriage prevails. In polygynous systems, in which men take several wives at the same time,
women tend to have more equal access to resources, such as land, food and shelter - - and parenting help. This is because women, or their parents
on their behalf, favor polygynous marriages with wealthy men who have
more resources to share.

Researchers observed something else in their work.

"It turns out that monogamous mating (and marriage) can drive significant inequalities among women," Borgerhoff Mulder said. Monogamy, practiced
in agricultural and market economies, can promote large differences in
the number of children couples produce, researchers found, resulting
from large differences in wealth in such economies.

How humans may differ The fact men are relatively egalitarian compared
to other animals reflects our patterns of child rearing. Human children
are heavily dependent on the care and resources provided by both mothers
and fathers -- a factor that is unusual, but not completely absent --
in other mammals, researchers said.

The critical importance of the complementary nature of this care --
that that each parent provides different and often non-substitutable
resources and care throughout long human childhoods -- is why we don't
show the huge reproductive variability seen in some of the great apes,
said researcher Paul Hooper, from the University of New Mexico.

To support these inferences, however, anthropologists need more empirical
data.

"In short, the importance of biparental care is grounded in our model,
but needs further testing," Borgerhoff Mulder said.

* RELATED_TOPICS
o Health_&_Medicine
# Children's_Health # Menopause # Pregnancy_and_Childbirth
# Fertility
o Plants_&_Animals
# Mating_and_Breeding # Nature # Wild_Animals #
New_Species
* RELATED_TERMS
o Horse_breeding o Mule o Zoo o Mammal o Hinny o Mite o
Giant_Panda o Plant_breeding

========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Karen
Nikos-Rose. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Cody T. Ross, Paul L. Hooper, Jennifer E. Smith, Adrian V. Jaeggi,
Eric
Alden Smith, Sergey Gavrilets, Fatema tuz Zohora, John Ziker,
Dimitris Xygalatas, Emily E. Wroblewski, Brian Wood, Bruce
Winterhalder, Kai P.

Willfu"hr, Aiyana K. Willard, Kara Walker, Christopher von Rueden,
Eckart Voland, Claudia Valeggia, Bapu Vaitla, Samuel Urlacher,
Mary Towner, Chun-Yi Sum, Lawrence S. Sugiyama, Karen B. Strier,
Kathrine Starkweather, Daniel Major-Smith, Mary Shenk, Rebecca
Sear, Edmond Seabright, Ryan Schacht, Brooke Scelza, Shane Scaggs,
Jonathan Salerno, Caissa Revilla-Minaya, Daniel Redhead, Anne
Pusey, Benjamin Grant Purzycki, Eleanor A. Power, Anne Pisor,
Jenni Pettay, Susan Perry, Abigail E. Page, Luis Pacheco-Cobos,
Kathryn Oths, Seung-Yun Oh, David Nolin, Daniel Nettle, Cristina
Moya, Andrea Bamberg Migliano, Karl J.

Mertens, Rita A. McNamara, Richard McElreath, Siobhan Mattison,
Eric Massengill, Frank Marlowe, Felicia Madimenos, Shane Macfarlan,
Virpi Lummaa, Roberto Lizarralde, Ruizhe Liu, Melissa A. Liebert,
Sheina Lew- Levy, Paul Leslie, Joseph Lanning, Karen Kramer, Jeremy
Koster, Hillard S. Kaplan, Bayarsaikhan Jamsranjav, A. Magdalena
Hurtado, Kim Hill, Barry Hewlett, Samuli Helle, Thomas Headland,
Janet Headland, Michael Gurven, Gianluca Grimalda, Russell Greaves,
Christopher D. Golden, Irene Godoy, Mhairi Gibson, Claire El Mouden,
Mark Dyble, Patricia Draper, Sean Downey, Angelina L. DeMarco,
Helen Elizabeth Davis, Stefani Crabtree, Carmen Cortez, Heidi
Colleran, Emma Cohen, Gregory Clark, Julia Clark, Mark A. Caudell,
Chelsea E. Carminito, John Bunce, Adam Boyette, Samuel Bowles,
Tami Blumenfield, Bret Beheim, Stephen Beckerman, Quentin Atkinson,
Coren Apicella, Nurul Alam, Monique Borgerhoff Mulder.

Reproductive inequality in humans and other mammals. Proceedings
of the National Academy of Sciences, 2023; 120 (22) DOI:
10.1073/pnas.2220124120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230523123756.htm

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