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Biology may play role in sibling rivalry

MANCHESTER, England, Dec. 20 (UPI) -- British biologists say a study of burying beetles determined parents have a biological tendency to favor their oldest child.

The University of Manchester report, published in the journal Ecology, supports the findings of studies carried out on human families, the university said in a news release.

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Lead researcher Per Smiseth said said the study of the burying beetle Nicrophorus vespilloides looked at how the parent beetles mediate competition between different age offspring.

"When both sets of grubs were left to fend for themselves they grew at the same rate and matured to an equal size," said Smiseth. "However, when we allow the parents to remain with the offspring, there is clear favoritism toward the older siblings, which grow at a faster rate as they take the lion's share of their parents' offerings."

The team said it may be that the parents attach more value to the older offspring because they have a better chance of survival than their younger siblings, or it could be that the older grubs are able to dominate their younger rivals and better attract the attention of the parents.

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