WEBVTT - Why Do Babies' Eyes Sometimes Change Color?

0:00:01.920 --> 0:00:06.800
<v Speaker 1>Welcome to brain Stuff, a production of iHeart Radio, Hey

0:00:06.840 --> 0:00:11.119
<v Speaker 1>brain Stuff, Lauren vogelbam here. Even outside of poetic or

0:00:11.200 --> 0:00:14.680
<v Speaker 1>psychological concepts of our eyes being windows to the soul

0:00:15.000 --> 0:00:20.560
<v Speaker 1>or to empathetic understanding humans, eyes are highly individual, a

0:00:20.760 --> 0:00:24.400
<v Speaker 1>unique part of every one of us. It's what technologies

0:00:24.440 --> 0:00:28.080
<v Speaker 1>like retinal scans and iris recognition rely on the idea

0:00:28.200 --> 0:00:30.640
<v Speaker 1>that the muscle, fibers and blood vessels that make our

0:00:30.640 --> 0:00:34.040
<v Speaker 1>eyes work are also so individual that they can work

0:00:34.120 --> 0:00:38.559
<v Speaker 1>like fingerprints, and they generally can. Though your eyes can

0:00:38.640 --> 0:00:42.680
<v Speaker 1>experience changes due to some diseases, medications, or the process

0:00:42.720 --> 0:00:45.960
<v Speaker 1>of aging over the course of your life. But if

0:00:46.000 --> 0:00:48.600
<v Speaker 1>you've ever hung out with a newborn through their first

0:00:48.680 --> 0:00:51.640
<v Speaker 1>birthday or so, you may have noticed that their eyes

0:00:51.840 --> 0:00:56.160
<v Speaker 1>completely changed color from blue to well, any other color.

0:00:57.760 --> 0:01:01.080
<v Speaker 1>Don't worry. There's no cause for alarm. Changing eye color

0:01:01.240 --> 0:01:04.679
<v Speaker 1>is a normal part of baby development. Anywhere from about

0:01:04.800 --> 0:01:07.440
<v Speaker 1>nine months to three years of age, a baby's eye

0:01:07.440 --> 0:01:11.400
<v Speaker 1>color sets on a relatively permanent hue as more melanin

0:01:11.560 --> 0:01:16.160
<v Speaker 1>is released into their eyes. When you notice someone's eye color,

0:01:16.360 --> 0:01:18.679
<v Speaker 1>you're looking at a part of the eye called the iris,

0:01:18.800 --> 0:01:21.560
<v Speaker 1>which is a fibrous ring that controls sides of the

0:01:21.560 --> 0:01:26.319
<v Speaker 1>people and contains melanin. Melanin is a pigment that gives

0:01:26.360 --> 0:01:30.360
<v Speaker 1>color to our hair, eyes, and skin. Our bodies don't

0:01:30.400 --> 0:01:33.720
<v Speaker 1>really step up melanin production to full levels until after

0:01:33.840 --> 0:01:36.919
<v Speaker 1>we're born. It can take several months to several years

0:01:37.000 --> 0:01:39.440
<v Speaker 1>for our skin and hair color to set to our

0:01:39.520 --> 0:01:43.399
<v Speaker 1>personal baseline. This is also why some babies born blonde

0:01:43.440 --> 0:01:47.400
<v Speaker 1>developed darker hair throughout childhood. Depending on the amount of

0:01:47.440 --> 0:01:52.200
<v Speaker 1>melanin in the iris, it can be shades of gray, green, hazel, amber, brown,

0:01:52.400 --> 0:01:54.880
<v Speaker 1>or even pink or red. Pink or red will occur

0:01:54.960 --> 0:01:57.960
<v Speaker 1>because of a condition called albinism, in which our cells

0:01:58.000 --> 0:02:02.040
<v Speaker 1>develop very little or no melanie. Without melanin, our irises

0:02:02.080 --> 0:02:04.680
<v Speaker 1>are clear, so the red we see is the blood

0:02:04.720 --> 0:02:09.600
<v Speaker 1>vessels inside the eye. And eye color isn't just for esthetics.

0:02:10.120 --> 0:02:12.800
<v Speaker 1>Like most of your biology, eye color has a purpose.

0:02:13.480 --> 0:02:16.840
<v Speaker 1>Thousands of years ago, the first humans all had brown eyes.

0:02:18.120 --> 0:02:20.840
<v Speaker 1>Just like the melanin in our skin cells protects against

0:02:20.880 --> 0:02:24.120
<v Speaker 1>the sun's damaging u V rays. Melanin in our eyes

0:02:24.160 --> 0:02:27.320
<v Speaker 1>can keep harmful rays from causing long term damage like

0:02:27.480 --> 0:02:32.400
<v Speaker 1>cataracts or rare types of eye cancer. As humans migrated

0:02:32.400 --> 0:02:35.840
<v Speaker 1>and settled in climates with less harsh sun exposure, they

0:02:35.919 --> 0:02:40.639
<v Speaker 1>required less melanin and human genetics adapted, though the most

0:02:40.680 --> 0:02:44.359
<v Speaker 1>common eye color is still brown across the world. Interestingly,

0:02:44.720 --> 0:02:47.920
<v Speaker 1>all melanin is brown. The more melanan and eye has,

0:02:48.200 --> 0:02:51.720
<v Speaker 1>the darker it will appear. In eyes that have less melanan,

0:02:52.120 --> 0:02:55.200
<v Speaker 1>like the ones that appear blue or green, less light

0:02:55.320 --> 0:02:58.160
<v Speaker 1>is absorbed by the iris, and that means that more

0:02:58.240 --> 0:03:01.040
<v Speaker 1>light is reflected and it's atters around the eye, and

0:03:01.080 --> 0:03:05.799
<v Speaker 1>a phenomenon called the Tindal effect. It's physically similar, though

0:03:05.880 --> 0:03:09.320
<v Speaker 1>not identical, to why the sky appears blue from light

0:03:09.400 --> 0:03:12.760
<v Speaker 1>scattering in the atmosphere, or why our veins appear blue

0:03:13.000 --> 0:03:17.359
<v Speaker 1>from light scattering through our skin. Of course, heredity plays

0:03:17.360 --> 0:03:20.720
<v Speaker 1>a role in eye color. A person's hereditary eye color

0:03:20.840 --> 0:03:23.720
<v Speaker 1>can be straightforward, such as when two parents with a

0:03:23.840 --> 0:03:27.800
<v Speaker 1>dominant brown eye gene have a brown eyed child. However,

0:03:27.960 --> 0:03:31.560
<v Speaker 1>research has identified sixteen genes that are involved in determining

0:03:31.600 --> 0:03:35.440
<v Speaker 1>a person's eye color. Two parents with a recessive blue

0:03:35.440 --> 0:03:38.280
<v Speaker 1>eye gene can have a child with brown eyes because

0:03:38.320 --> 0:03:43.000
<v Speaker 1>of modifier genes or mutations. Gene mutations occur when genes

0:03:43.040 --> 0:03:47.600
<v Speaker 1>are misspelled or turned off due to environmental conditions or disease.

0:03:48.560 --> 0:03:52.119
<v Speaker 1>The point is genetics are complicated, but it's why you

0:03:52.160 --> 0:03:54.960
<v Speaker 1>are the only person in the world with your eyes,

0:03:55.920 --> 0:03:58.000
<v Speaker 1>and so go ahead and take a longer look in

0:03:58.000 --> 0:04:01.760
<v Speaker 1>the mirror. Today. Your eyes tell a unique, thousands year

0:04:01.800 --> 0:04:05.440
<v Speaker 1>old story that started with your ancestors and now includes you.

0:04:11.960 --> 0:04:14.640
<v Speaker 1>Today's episode is based on the article why do babies

0:04:14.680 --> 0:04:17.279
<v Speaker 1>Eyes Change color? On how stuff works dot com, written

0:04:17.320 --> 0:04:19.919
<v Speaker 1>by Alison Troutner. Brain Stuff is a production of I

0:04:20.000 --> 0:04:22.200
<v Speaker 1>Heart Radio in partnership with how stuff works dot Com,

0:04:22.240 --> 0:04:25.000
<v Speaker 1>and it's produced by Tyler Klang and Ramsey Young. Four

0:04:25.040 --> 0:04:27.240
<v Speaker 1>more podcasts from my heart Radio. Visit the I heart

0:04:27.320 --> 0:04:30.040
<v Speaker 1>Radio app, Apple Podcasts, or wherever you listen to your

0:04:30.080 --> 0:04:30.760
<v Speaker 1>favorite shows.