Are Relative's Fingerprints Similar?
Camila Solano Zambrano
I think that, although there are no two fingerprints in the world that are the same, there could be some sort of similarity between family members; these similarities might arise because of genes, DNA, or other biological elements that parents could share with their children.
So, my hypothesis is that there might be some similarities between family fingerprints.
First, what is a fingerprint? Fingerprints are basically impressions left by ridges on the human finger. Fingerprints are a big part of forensic science. What makes a fingerprint unique are the dead ends, forks, and paths in the print. But apparently, a study shows that, even though the chances of a match are 1 in 64 billion, there are about 100 billion people who have ever lived on Earth. So even though it’s highly unlikely, so is winning the lottery, but people do that very often.
In fetal development, lumps of stem cell tissues –called volar pads- grow under the skin on each finger. Whether the volar pad is small, big, off to the side, or grows unevenly, determines the main pattern of the fingerprints. On top of volar pads, the embryonic skin has several layers of cells, all growing at different rates. And as the inner layer grows, the middle layer buckles, causing the ridges to form in the upper layer.
There are more than these three types of fingerprints though, examples being the double loop whorl, central pocket loop, and the ulnar loop.
The independent variable was the fingers, as I could pick which ones I wanted to use. The controlled variable was the subjects/family. The dependent variable was the score of the match.
At first glance, what I noticed was that the comparisons against the same finger for a given subject were always the highest score.
I have seen that the Siblings [S(F) and S(M)] have the highest scores. However, the male sibling shows consistently the highest scores.
Among the parents, the female [P(F)] usually shows a slightly higher score compared to the male [P(M)].
All the cross-comparison scores are low relative to the self-comparisons.
Again, the siblings have most of the higher scores, but the male sibling vs. the female parent also have some high scores in the two bottom graphs.
The comparison between the female sibling and either of the parents shows the lower scores (for the most part). However, most of the lower scores involve the male parent.
I think that the children have a higher score because of the elasticity of their skin, which you lose as you get older. If you have less elasticity, then it will be harder to take your fingerprint, and as you age, it might get slightly altered.
The conclusion from these graphs is that the fingerprints are more similar between siblings. There is some degree of similarity between the children and the mother. And there is less similarity between the children and the father.
Fingerprints on a child’s hand show more similarity compared to fingerprints on adult hands.
The cause of this might be because of the elasticity in people’s skin, which gradually fades as you get older.
Fingerprints are more similar between siblings. There is some degree of similarity between the children and the mother. But the lowest similarity was found between the children and the father.
Even though fingerprint experts can disagree, most of them think that a score of 8-12 points is needed to make a match. As shown on the siblings’ matrix, the score ranges between 7 and 12.5 points (excluding the self-matrixes).
Therefore, if- for example- one of the subjects commits a crime, and their fingerprints are found on the scene, and they take the other subject’s fingerprints, then the court could end up identifying a false positive.
Potential applications of my project are:
1) For people who don't just like to see facts, but want to see proof that they are true.
2) For people who can't afford DNA, blood, or other tests used to find "long-lost relatives".
Sources Of Error
Potential sources of error could be: 1) Data collection, as some fingerprints might not have been taken entirely. 2) The number of samples is relatively low (only one family); adding more families could increase the statistical representation of the experiment.
I used multiple links and websites for this project.
My acknowledgements would be the CSIpix program vendors, as it was on a free trial for 30 days and I didn't have to pay for it. And also my family, for helping and supporting me during the science fair.