SciBites: Week of March 10th

SciBites: Week of March 10th

Mathematical model may reveal how big brains evolved

How did large brains evolve in humans and other animals? A new mathematical model study published in PLOS Computational Biology may help clarify what drove the evolution of big brains. The model predicts how large the human brain should be at different stages of an individual’s life, depending on different possible evolutionary scenarios. The researchers examined the ecological factors that might influence brain growth, using the model to test the scenario of a human hunting for food alone, but receiving help from its mother while young. In that specific scenario, the hypothetical human brain grew as big as ancient humans’ brains are thought to have grown, and the slow growth rate matched that of modern human brains. This runs counter to prevailing thought, which holds that social and cultural influences are required to achieve these sizes and growth rates, although the team hopes to next use the model to test how social and cultural factors may affect brain growth.

Leaf-cutting ants can learn to identify unsuitable plants without leaving the colony dump

Leaf-cutting ants harvest leaf fragments and carry them back to their nests, using them to grow a fungus that is their main food source. If a plant proves unsuitable for growing fungus, however, they stop collecting it. The authors of a recently published study investigated how ants learn to identify unsuitable plants by feeding fungicide-treated plants to ants and collecting plant waste later discarded by the ants due to the poor fungus growth. They then exposed this waste to other ants that had only been fed untreated plants of the same type and found that it made the ants avoid these plants. This suggests that cue within the colony’s waste dump are enough for ants to learn which plants are not suited for growing fungus.

Incidence of dementia increased in the Netherlands over 23 years

In a recent PLOS Medicine study, researchers collected data on dementia diagnoses in the Netherlands for the years 1992 to 2014. General practitioner networks provided electronic health record data on more than 800,000 people aged 60 years and over, including 23,186 cases of newly diagnosed dementia. The researchers estimate that dementia incidence increases by 2.1 percent annually, with incidence rates 1.08 times higher for women compared to men. The authors say that increased awareness of dementia by patients and doctors in more recent years may have influenced diagnosis rates and needs to be taken into account when interpreting the data. In an accompanying Perspective, Eric Larson says, “We must plan for increasing numbers of predominantly older people with dementia in the decades to come, including addressing the growing need for long-term care in the context of a significant decline in the availability of family caregivers.”

Image Credit: Tim Evanson

Author

Tessa is an Editorial Media Associate at PLOS. She graduated from the University of California, Berkeley with degrees in Rhetoric and Music. She can be reached by email at tgregory@plos.org and on Twitter at @tessagregs.

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