Since pretty much the dawn of time, women have been assaulted with unrealistic beauty standards to which we're pressured to conform. The problem is, the only thing that's constant about the "perfect female body" is the standard is always changing. Back in the Renaissance era, the ideal woman was curvy and pale with a round face. \n\nIt's safe to say that's changed many times since, proving that "the perfect female body" doesn't actually exist. One Instagram influencer was determined to show just how much the ideal female body has changed over the last 100 years.This is Sia.Sia is a personal trainer, a mom, and she has over a million followers on Instagram. She recently posted a series of photos she called, "The Perfect Female Body Through the Decades," in which she uses her own body to display the ideal features of the female form from the 1920s through to today. \n\nThe effect of this photo series is striking. It amplifies the idea that, in a mere 10 years, an entire standard of beauty can change, which can and does cause women to develop unhealthy views of their own bodies and judge themselves way too harshly.The Roaring '20sAbout the ideal body type of the 1920s, Sia writes, "This body style was all about boyish. Women even opted for short hair. Boobs and waists didn’t matter and women felt liberated as they were." \n\nThe flapper ideal was slim, flat-chested, and boxy with a "downplayed waist." But 30 years later, things were completely different.Hollywood Era '50sAccording to Sia, in the 1950s, "Women focused on curves — think Marilyn Monroe. They didn’t care about weight, but a slimmer waist was ideal. Playboy was also introduced in this era." \n\nThat big boob, hourglass, Marilyn Monroe figure really became the ideal in the 1950s.Swinging '60s and '70sOnce we reached the '60s and '70s, we were back to thinking small waists and lanky, thin bodies were the ideal. "This was the area of the 'twig' body style thanks to famous model Twiggy," Sia writes. "Women wanted a thin and girly, adolescent appearance."Supermodel '80sBy the '80s, that thin, "twiggy" body traded in for the athletic, curvy bodies of '80s supermodels. A new and different unattainable ideal! Sia writes, "Catwalks and supermodels became the it thing. Think Naomi Campbell abs. Cindy Crawford. Lean and tall legs and an athletic body type were ideal. This was also when fitness started hitting big."Heroin Chic '90sThe super thin, waifish "heroin chic" ideal of the '90s was real. This "heroin chic" ideal always makes me think of the terrible idea Judy Greer's character pitches to Poise magazine in 13 Going on 30 (a perfect movie). \n\nSia writes, "The waif look took over once Kate Moss took the world by storm. This gaunt malnourished look was the thing as well as appearing androgynous — neither female or male. CK One was also created during this time."Postmodern Beauty of TodaySia says it best herself: "It’s the era of @jlo and the Kardashians, where big boobs and butts and flat tummies are on the rise. Women also turn to plastic surgery to achieve their desired look. Women are unhappier than ever with their appearance. \n\n"It’s no wonder why we are all so obsessed and screwed up with our self appearances. We’ve let society tell us how to look for YEARS — it’s nothing new. \n\n"If you want to be truly happy, focus on self acceptance and body love. Make this the decade you choose to forget what the media says and choose to love your own self as you are."