scholarly journals A feedback loop able to enlarge the brain for 2.4 myr without Darwin’s selective survival

2016 ◽  
Author(s):  
William H. Calvin
Keyword(s):  
Fire Ecology ◽  
Feedback Loop ◽  
Brain Size ◽  
Evolutionary Process ◽  
Homo Erectus ◽  
Burn Scar ◽  
The Core ◽  
Selective Survival ◽  
Boom And Bust ◽  
Evolutionary Emergence

The rapid three-fold enlargement of the hominin brain1,2 began about 2.3 million years ago (myr) as Africa dried and grass replaced brush, creating great savannas3. Seeking an amplifying feedback loop, I analyzed the lightning-brush-fire ecology for grazing animals in a grassy burn scar4. Discovering the new grass by exploring brush byways could promote a population boom–but only after grass-specialized herbivores evolved from mixed feeders5 at 2.4 myr. When the brush returned several decades later, the grazer boom would turn to bust, squeezing numerous descendants back into the core grasslands. Meat-eating Homo species would boom and bust when grazers did, enriching the core in whatever alleles were earlier concentrated in the brush fringe catchment zone for that boom. This return migration for Homo is what creates the amplifying feedback loop that speeds brain enlargement rate, likely up to the mutation rate limit. It also promotes trait hitchhiking: any brush-relevant allele, not just those for hunting, can experience amplifying feedback merely by hanging out in the catchment zone4. The shade offered by brush would have been the default location for cooperative nurseries, time-consuming food preparation, and toolmaking. Increased behavioral versatility correlates with larger brain size and the more versatile brains of a current generation need only spend more-than-average time in the boom’s catchment zone for this recursive evolutionary process to keep average brain size increasing via assortative mating. This helps account for the time when enlargement began, why it was linear, when it ended, and why it slowed in Neanderthals and in Asian Homo erectus. Without utilizing Darwin’s selective survival, the feedback loop makes advance room for “free” future functionality in the cerebral cortex, likely relevant to the evolutionary emergence of our structured intellectual functions6 such as syntax, contingent planning, games, and logic.

scholarly journals Hitchhiking on the Frontier: Accelerating Eusociality and other Improbable Evolutionary Outcomes by Trait Hitchhiking in a Boom-and-Bust Feedback Loop

2016 ◽  
Author(s):  
William H. Calvin
Keyword(s):  
Feedback Loop ◽  
Feedback Loops ◽  
Early Pleistocene ◽  
Lightning Strike ◽  
Gene Frequencies ◽  
Burn Scar ◽  
Fire Cycle ◽  
The Core ◽  
Selective Survival ◽  
Boom And Bust

AbstractHere I analyze the brush-fire cycle behind the brushy frontier of a grassland, seeking evolutionary feedback loops for large grazing animals and their hominin predators. Several months after a lightning strike, the burn scar grows enough new grass to expand the carrying capacity for grass-specialized herbivores,which evolved from mixed feeders in Africa during the early Pleistocene. The frontier subpopulation of grazers that discovers the auxiliary grassland quickly multiplies,creating a secondary boom for its hominin predators as well. Following this boom, a bust occurs several decades later when the brush returns; it squeezes both prey and predator populations back into the core grassland. This creates a feedback loop that can repeatedly shift the core’s gene frequencies toward those of the frontier subpopulation until fixation occurs. Any brush-relevant allele could benefit from this amplifying feedback loop, so long as its phenotypes concentrate near where fresh resources can suddenly open up, back in the brush. Thus, traits concentrated in the frontier fringe can hitchhike; improved survival is not needed. This is natural selection but utilizin selective reproductive opportunity instead of the usual selective survival. Cooperative nurseries in the brush’s shade should concentrate the alleles favoring eusociality, repeatedly increasing their proportion via trait hitchhiking in the feedback loop.

scholarly journals In Rift Valley settings with a feedback loop, assortative mating for versatility predicts hominin brain enlargement in some detail

2017 ◽  
Author(s):  
William H. Calvin
Keyword(s):  
Assortative Mating ◽  
Rift Valley ◽  
Feedback Loop ◽  
Homo Sapiens ◽  
Brain Size ◽  
Cosmic Ray ◽  
Homo Erectus ◽  
Gene Frequencies ◽  
Burn Scar ◽  
Boom And Bust

AbstractHominin procedures for fire-starting, sharpening rocks, and softening roots by pounding or chopping require sustained attention for hours; shade is sought in the brush fringe bordering a grassland. Clustering these more versatile adults, while others are away hunting and gathering, provides a setup for assortative mating. This can lengthen attention span, enhance versatility and, with it, brain size. The rate of enlargement is accelerated by a boom-and-bust cycle in their meat supply, predicting the observed initiation of enlargement at −2.3 myr in the Rift Valley once boom-prone grazers evolved from the mixed feeders. Several months after lightning created a burn scar back in the brush, the new grassland enables a population boom for those grazers that discover it. Several decades later as brush regrows, they are pushed back. Their hominin followers, wicked in from the grassland’s shady fringe, boom together with the burn-scar grazers. They then follow their meat supply back to the main population. This creates an amplifying feedback loop, shifting Homo gene frequencies centrally. Brush fires are so frequent that the cosmic ray mutation rate becomes enlargement’s rate-limiter, consistent with 460 cm3/myr remaining constant during many climate shifts. The apparent tripling of enlargement rate in the last 0.2 myr vanished when the non-ancestors were omitted. Asian Homo erectus enlargement lags the ancestral trend line by 0.5 myr. Neanderthals lag somewhat less but have a late size spurt after the −70 kyr Homo sapiens Out of Africa, suggesting enlargement genes were acquired via interbreeding.

Future Directions of Course Management Systems

2011 ◽  
pp. 307-330
Author(s):  
David Mills
Keyword(s):  
Higher Education ◽  
Teaching And Learning ◽  
Data Exchange ◽  
Evolutionary Process ◽  
Management Systems ◽  
Course Management Systems ◽  
Course Management ◽  
Future Directions ◽  
The Core ◽  
Core Mission

Course management systems will unquestionably become one of the most critical enterprise systems in higher education. This is because these systems are more closely aligned with the core mission of teaching and learning than any others. Although these systems have already undergone extraordinary transformation in just a few short years, we are at only the very beginning of the evolutionary process. It is critical that CMS vendors look to the students, educators, and administrators that interact with these systems to identify what new tools and features they need. Consequently, the next stage of innovation in course management systems should therefore focus more on features specifically related to promoting better and more efficient processes for teaching and learning online. More flexible administration options should make these systems easier to maintain. Emerging standards will continue to simplify communications and data exchange with other systems. Finally, the infusion of sound principles of instructional design and learning theory into the tools themselves promises to transform today’s course management systems into tomorrow’s expert systems for teaching and learning.

High Power Actuator Based on Magnetostrictive Composite Core with Temperature Drift Compensation

2014 ◽  
Vol 598 ◽  
pp. 69-74 ◽  
Author(s):  
Jerzy Kaleta ◽  
Krzysztof Kot ◽  
Rafał Mech ◽  
Przemyslaw Wiewiorski
Keyword(s):  
Magnetic Field ◽  
Pid Control ◽  
Feedback Loop ◽  
Initial Conditions ◽  
Signal Generation ◽  
Temperature Drift ◽  
Fiber Bragg Grating Sensors ◽  
The Core ◽  
Drift Compensation ◽  
Initial Settings

The paper presents an actuator based on a coil placed in the casing, with specially prepared connection rods. The construction allows installation of the fiber Bragg grating sensors inside the coil. It allows to measure deformation of the composite that is located in the core of the coil. Thanks to the signal generation with use of DASYLab software, it is possible to precisely control the frequency, value of amplitude excitation and to send the signal to the system with use of the measurement card. The main goal of the experiment is to keep constant value of deformation, by means of a feedback loop with use of PID control, and to change the initial conditions of the test by change of the external force. The system is designed to return to the initial settings by appropriate control of the intensity of magnetic field, and thus the deformation of the sample.

scholarly journals Cross-Cohort Analysis Identifies a TEAD4–MYCN Positive Feedback Loop as the Core Regulatory Element of High-Risk Neuroblastoma

2018 ◽  
Vol 8 (5) ◽  
pp. 582-599 ◽  
Author(s):  
Presha Rajbhandari ◽  
Gonzalo Lopez ◽  
Claudia Capdevila ◽  
Beatrice Salvatori ◽  
Jiyang Yu ◽  
...  
Keyword(s):  
High Risk ◽  
Positive Feedback ◽  
Feedback Loop ◽  
Regulatory Element ◽  
Cohort Analysis ◽  
Positive Feedback Loop ◽  
The Core

scholarly journals Integrin-mediated Cell Attachment Induces a PAK4-dependent Feedback Loop Regulating Cell Adhesion through Modified Integrin αvβ5 Clustering and Turnover

2010 ◽  
Vol 21 (19) ◽  
pp. 3317-3329 ◽  
Author(s):  
Zhilun Li ◽  
John G. Lock ◽  
Helene Olofsson ◽  
Jacob M. Kowalewski ◽  
Steffen Teller ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Strength ◽  
Feedback Loop ◽  
Cell Attachment ◽  
Growth Factor Signaling ◽  
The Core ◽  
Matrix Adhesion ◽  
Mediated Effects ◽  
Cell Matrix ◽  
Regulatory Feedback Loop

Cell-to-extracellular matrix adhesion is regulated by a multitude of pathways initiated distally to the core cell–matrix adhesion machinery, such as via growth factor signaling. In contrast to these extrinsically sourced pathways, we now identify a regulatory pathway that is intrinsic to the core adhesion machinery, providing an internal regulatory feedback loop to fine tune adhesion levels. This autoinhibitory negative feedback loop is initiated by cell adhesion to vitronectin, leading to PAK4 activation, which in turn limits total cell–vitronectin adhesion strength. Specifically, we show that PAK4 is activated by cell attachment to vitronectin as mediated by PAK4 binding partner integrin αvβ5, and that active PAK4 induces accelerated integrin αvβ5 turnover within adhesion complexes. Accelerated integrin turnover is associated with additional PAK4-mediated effects, including inhibited integrin αvβ5 clustering, reduced integrin to F-actin connectivity and perturbed adhesion complex maturation. These specific outcomes are ultimately associated with reduced cell adhesion strength and increased cell motility. We thus demonstrate a novel mechanism deployed by cells to tune cell adhesion levels through the autoinhibitory regulation of integrin adhesion.

scholarly journals Distinct Roles of HDAC3 in the Core Circadian Negative Feedback Loop Are Critical for Clock Function

Cell Reports ◽  
2016 ◽  
Vol 14 (4) ◽  
pp. 823-834 ◽  
Author(s):  
Guangsen Shi ◽  
Pancheng Xie ◽  
Zhipeng Qu ◽  
Zhihui Zhang ◽  
Zhen Dong ◽  
...  
Keyword(s):  
Negative Feedback ◽  
Feedback Loop ◽  
Negative Feedback Loop ◽  
The Core

scholarly journals E2F1 Induces KIF26A Transcription and Promotes Cell Cycle Progression via CDK–RB–E2Fs Feedback Loop in Breast Cancer

2021 ◽  
Vol 10 ◽  
Author(s):  
Jing Xu ◽  
Lei Liu ◽  
Ranran Ma ◽  
Yawen Wang ◽  
Xu Chen ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Cycle ◽  
Cell Proliferation ◽  
Feedback Loop ◽  
Cell Cycle Progression ◽  
Transcriptional Factor ◽  
Phase Cell ◽  
Luciferase Reporter ◽  
Cycle Progression ◽  
The Core

ObjectiveThe aim of this study was to investigate the role of KIF26A in breast cancer.MethodqRT-PCR and immunohistochemistry were conducted to explore KIF26A expression and functional contribution to breast cancer development. MTS, EDU, colony formation assays, and flow cytometry analysis were conducted to assess cell proliferation characteristics and cell cycle progression. A series of 5′-flanking region deletion plasmids and mutating the binding site, with the luciferase reporter assay, were used to identify the core promotor region of KIF26A. The prediction by software and construction of the transcriptional factor plasmids were used to identify the transcriptional factor. Chromatin immunoprecipitation assay could demonstrate transcriptional factor directly binding to the KIF26A promoter. Human Genome Oligo Microarray Assay and gene ontology (GO) and pathway analyses were used to predict the downstream pathway.ResultsOur results showed that in breast cancer tissues, elevated KIF26A expression was significantly correlated with lymph node metastasis. KIF26A could promote proliferation and G0/G1 phase cell cycle progression in breast cancer cells. The core promoter region of the human KIF26A gene was located upstream of the transcription start site at position −395 to −385. The transcriptional factor E2F1 was shown to activate KIF26A expression. Furthermore, KIF26A was shown to inhibit the expression of p21, then activate CDK–RB–E2Fs pathway. The elevated E2F1 can activate the cell cycle progression and the KIF26A expression, forming feedback loop.ConclusionsThe present study demonstrated that KIF26A, directly upregulated by E2F1, promoted cell proliferation and cell cycle progression via CDK–RB–E2Fs feedback loop in breast cancer.

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