We feel more altruistic to those who resemble us because in the past our early ancestors assumed that they were related, according to the study.
The instinct dates back to when there were no mirrors and people could learn what their kin looked like only by inspecting the faces of household members.
The study, published in Biology Letters, even found that we were more naturally drawn to people who looked like us than our own relatives, if the resemblance was strong enough.
The researchers came to the conclusion after a study of 70 identical adult twins who, although genetically the same, had over the years grown to look different from each other.
Then they manipulated the photographs of the participants by digitally mixing them with a model’s face so that the images would either resemble them or their co-twin.
Then they asked each one who they would prefer to rescue from danger and which one they would prefer a different sex sibling to marry.
In each case, the person most resembling themselves was preferred almost two thirds of the time—significantly higher than being down to chance alone.
Dr Paola Bressan, of the University of Padova, Italy, said: “Our work shows a stranger who resembles us elicits pro-social regard more than a stranger who resembles a close family member—even one as close as our identical twin, who is, incidentally, genetically identical.”
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As a poet once said,
The Stranger within my gate,
He may be true or kind,
But he does not talk my talk --
I cannot feel his mind.
I see the face and the eyes and the mouth,
But not the soul behind.
The men of my own stock
They may do ill or well,
But they tell the lies I am wonted to.
They are used to the lies I tell,
And we do not need interpreters
When we go to buy and sell.
The Stranger within my gates,
He may be evil or good,
But I cannot tell what powers control
What reasons sway his mood;
Nor when the Gods of his far-off land
Shall repossess his blood.
The men of my own stock,
Bitter bad they may be,
But, at least, they hear the things I hear,
And see the things I see;
And whatever I think of them and their likes
They think of the likes of me.
This was my father's belief
And this is also mine:
Let the corn be all one sheaf --
And the grapes be all one vine,
Ere our children's teeth are set on edge
By bitter bread and wine.
-Rudyard Kipling
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